Broken link building may perhaps be the most effective, white-hat link building strategy in years. In particular, broken link building is appealing because the success of the campaign is directly proportional to how much good you do for the web. You profit only if you create good content to replace lost or abandoned content that webmasters still want to link to. This is the type of strategy that marries so many of the competing interests our industry: content vs. links, link earning vs link building, inbound vs. outbound, etc.

Below, I attempt to organize as much as I know about broken link building tactics. Throughout the piece I mention tools that will help you make the broken link building process scalable and less monotonous. Let's begin.
Table of Contents
Overview
Prospecting
Resource Page Targeting w/ Keywords
Selecting Keywords
Prospecting Phrases
Scraping Search Results
Extracting URLs
Header Checks
Opportunity Qualification
Prospecting Tools
Resource Page Targeting w/ Model URL
Site Selection
Backlink Acquisition
Extracting URLs
Header Checks
Opportunity Qualification
Prospecting Shortcuts
Direct URL Targeting
Site Crawling
Opportunity Selection
Content Creation
Rebuilding Tools
Raised Expectations
Outreach
Contact Finding
Email Templates
Conclusions & Community
Credits
Overview

Broken link building is a link building tactic where a marketer contacts a webmaster who has a broken link on his/her site and recommends one or more alternatives that include his/her target site. For the purposes of this piece, we will use a pediatrician in Raleigh, NC as an example client.
Prospecting

The first step in any Broken link building campaign is to find relevant dead pages. However, there are different methods of prospecting depending upon the broken link building strategy you are employing. There are essentially three types of broken link building strategies:
Resource Page Targeting with Keywords
Resource Page Targeting with URLs
Direct URL Targeting

We will cover each of these in the prospecting section. I will mention multiple tools throughout this post and will give descriptions of all of them at the end.
Keyword Based

Keyword based is the the most common and, in my opinion, straightforward method of broken link building. The method involves searching Google for keywords relevant to your site's interests, finding resource pages that link to content related to your keywords, extracting all the links from those resource pages, finding missing pages among those links, and finally qualifying those opportunities.

Select Prospecting Keywords Like so many things in SEO, we begin with keyword selection. A successful broken link building campaign lives and dies by the keywords used. There are a couple of characteristics we want to look for in an ideal keyword.
Categorically relevant: This characteristic seems obvious. The prospecting keywords need to be relevant. However, they don't necessarily have to be relevant to your product like the key phrase "health resources." The keywords could be relevant to your audience "resources for kids" or your geography "Raleigh resources." Remember, you are finding resource pages with these keywords, you are not finding the final targets. You want to cast a wide net, which leads to...
Generally broad: This is where most campaigns fail. Our mock client is unlikely to find any resource pages for the keyword "raleigh nc pediatrician resources," much less any with good link opportunities. You should choose key phrases that you would consider to be categories that your company might fall in, rather than the specific term.

Prospecting Phrases: Once you have identified your keywords, you will want to pair them with prospecting phrases. These are searches to use in Google or Bing to find relevant resource and links pages like "intitle:resources" or "inurl:links." Below is a list of prospecting phrases you can use to help find relevant linking pages.
site:.gov
links
resources
intitle:links
intitle:resources
intitle:sites
intitle:websites
inurl:links
inurl:resources
inurl:sites
inurl:websites
"useful links"
"useful resources"
"useful sites"
"useful websites"
"recommended links"
"recommended resources"
"recommended sites"
"recommended websites"
"suggested links"
"suggested resources"
"suggested sites"
"suggested websites"
"more links"
"more resources"
"more sites"
"more websites"
"favorite links"
"favorite resources"
"favorite sites"
"favorite websites"
"related links"
"related resources"
"related sites"
"related websites"
intitle:"useful links"
intitle:"useful resources"
intitle:"useful sites"
intitle:"useful websites"
intitle:"recommended links"
intitle:"recommended resources"
intitle:"recommended sites"
intitle:"recommended websites"
intitle:"suggested links"
intitle:"suggested resources"
intitle:"suggested sites"
intitle:"suggested websites"
intitle:"more links"
intitle:"more resources"
intitle:"more sites"
intitle:"more websites"
intitle:"favorite links"
intitle:"favorite resources"
intitle:"favorite sites"
intitle:"favorite websites"
intitle:"related links"
intitle:"related resources"
intitle:"related sites"
intitle:"related websites"
inurl:"useful links"
inurl:"useful resources"
inurl:"useful sites"
inurl:"useful websites"
inurl:"recommended links"
inurl:"recommended resources"
inurl:"recommended sites"
inurl:"recommended websites"
inurl:"suggested links"
inurl:"suggested resources"
inurl:"suggested sites"
inurl:"suggested websites"
inurl:"more links"
inurl:"more resources"
inurl:"more sites"
inurl:"more websites"
inurl:"favorite links"
inurl:"favorite resources"
inurl:"favorite sites"
inurl:"favorite websites"
inurl:"related links"
inurl:"related resources"
inurl:"related sites"
inurl:"related websites"
list of links
list of resources
list of sites
list of websites
list of blogs
list of forums



Search Results Scraping: You now have the arduous task of finding all the results for all these prospecting phrases. Google is not fond of sending in automated requests, so you have a couple of choices. You complete the task by hand and use the MozBar to extract results, you can use a SERP scraping tool and risk Google's ire, or you could look into use the Bing API, which would necessitate changing many of the search operators in the above list of prospecting phrases. Ultimately, you will want to pull down the top 100 results for each of the prospecting phrases you use. You will have quite a bit of crossover, so you will want to de-dupe those lists. You can use Virante's free "Duplicate Deleter" tool to accomplish this, or you can simply use Excel's remove duplicates function.

Link Extraction: Once you have a culled list of potential "linking pages," you need to extract every external link from these pages and begin the process of finding all the 404s. You can also combine this step with the 404 header check using a tool like Domain Hunter+or Check My Links.

Link extraction:
webmaster-toolkit.com
iwebtool.com
code.google.com

Link extraction and 404 header check
Domain Hunter Plus
Check My Links

404 / Error Checking: Once you have extracted all the links, you will have to check the headers on each link to determine whether or not they are 404s, our ultimate target. If you used Domain Hunter Plus or Check My Links, you can skip this process. The easiest way to do this is with a simple HTTP Status Code checker. There is a free bulk tool here. Just copy and paste all your URLs here, without the http:// and it will find all the 404s for you.

Opportunity Qualification: There are two things you will want to determine about each potential opportunity to vet them for quality: relevance and backlinks.
Backlink acquisition: Once you have found a set of 404 pages, you now have to filter them to determine which are actually strong targets. The more backlinks pointing to a 404 page, the more opportunities you have for link replacement. These linking domains will be the sites you contact to replace the broken link with your own. There are several ways to do this, but the easiest at the moment is likely Majestic SEO's bulk backlink checker. Remember, at this point you are trying just to get an idea of those with the most links and ignore those with very few. This will limit the amount of time you have on checking relevance.
Relevance analysis: Now you filtered your list of 404 opportunities to those with a good number of unique linking domains. Let's say that number is 50 or more. You now have to determine the relevancy of that content. You can do that a few ways:
Visit the Wayback Machine (also known as the way back machine) to find cached copies of the URL in history. If the page is well linked and did not block web crawlers, you should be able to find the content here.
If this is not available, you can look at the anchor text of the links pointing to the page. You can use SEOMoz Open Site Explorer to get an export of the anchor text.
You can look at the URL itself for hints as to how relevant the content would be.
You can visit the linking pages to see if those links have descriptions of what the previous content was.

Prospecting Shortcuts: There are two tools that you could use to jump over a lot of these steps.
Broken Link Index (brokenlinkindex.com): This tool by iAcquire allows you to find tons of potential 404 pages from their gigantic database of opportunities. Unfortunately, all of the link qualifications have to be done one at a time, although you could export the list and automate the process if you are savvy.


Broken Link Builder (brokenlinkbuilding.com): This tool by CitationLabs is not free, but allows you to perform all of the actions above in an automated fashion. Just type in your kewords and it performs all of the steps above, from finding opportunities to qualifying them based on links and relevance. This is by far the most robust broken link building tool currently available and a huge time saver.



Resource Page Targeting w/ Model URL

Unlike using keywords, this method starts with a known site and mines their backlinks to relevant resource pages that, in turn, produce broken link building opportunities.

Site / URL Selection: This is by far the most important part of the process. Choosing the right site will make or break this strategy. I do want to give a nod to Garrett French for pointing this method out to me a few months ago. There are a couple of factors you want to use in identifying the perfect site or URL.
Non-commercial: In most cases, you want a non-commercial source. If the site has a direct incentive to acquire links, chances are there will be too much manipulated link noise in their backlink profile to properly mine them for broken link building opportunities.
Authoritative: If the site is not authoritative, it likely has attracted few links from resources that aggregate important links on the web. These are the resource pages from which we will find 404 opportunities. If they aren't linking to your selected URL, you are wasting your time.
Relevant: Obviously, the site needs to be relevant to your industry. You can use this technique to find great opportunities based on nasa.gov, but unless you are SpaceX, you probably have no business doing so.

Backlink Acquisition: Following the example above of a Raleigh, NC dentist, let's assume that we selected the American Dental Association (ADA.org). Using Open Site Explorer, Majestic SEO, or A Hrefs, export all of the links pointing back to this site. This list of URLs should be treated in the same way as the list of URLs in the keyword method that were pulled from searching Google with prospecting phrases. You can now skip to the Link Extraction section in the previous description and follow from there. The steps are identical, no need to repeat them.

Direct URL Targeting

This is the least scalable of the strategies and is used specifically to target a single link prospect. Unlike the previous two methods where you are trying to find potential broken content to replace and your link prospects are those who link to that broken content, in this method you have already chosen your link prospect and you simply want to find broken links on his/her site as an excuse to start a conversation. I hesitate to include this strategy because it is weak and unscalable, but it is a part of the grouping of strategies known as "broken link building" so I will include it.

Let's assume that you are the Raleigh, NC dentist and you have decided that all you really want is a link from ADA.org. You feel that you have some great content they would link to if only you had a reason to open up a conversation that didn't sound completely like begging. Well, the first step is to try and find a broken link on their site so you have a reason to reach out to their webmaster.

Site Crawling: Site crawling can be problematic because you must balance your need for relatively quick responses and a general respect for the site owner's bandwidth and uptime. Do not turn on a crawler that you are not certain follows polite crawling policies and obeys robots.txt. Your best bet would be one of the following:
Xenu Link Sleuth
A classic SEO tool, Xenu Link Sleuth makes it easy to spider a site and find broken links among other problems.
Screaming Frog SEO
Quickly becoming the spider of choice for many SEOs, Screaming Frog can quickly spider your site to diagnose everything from duplicate content to 404s.
Deep Trawl
Often overlooks, Deep Trawl is a worthy adversary for solving on-site issues.



Opportunity Selection: You now have a list of broken links on your ideal linking website. Identifying the best opportunity will greatly increase the likelihood of succeeding with this strategy. Here are a couple of pointers.
Choose a broken link opportunity where the link is external. This does two things: it makes the webmaster feel like it is not his/her fault unlike an internal link and it creates a 1:1 ratio of removing an external link and hopefully adding your external link. A webmaster is far more likely to replace a broken external link with another external link than to replace an internal link with an external one.
Try and choose a broken link on the same page as the one your link would most fit. This is most likely to occur if your ideal linking site has a resources section.

Content Creation

The next step in the broken link building process is creating content that matches or improves upon the broken page. The first step you will need to take is actually determining what the broken page is. We assume that you have already vetted this page for relevance so you should have a general idea, but getting as specific as possible will help you create content that meets the expectations of all of those who previously linked to the now defunct resource. There are two tools that can help with this right off the bat...

Rebuilding Tools:
Wayback Machine: The Wayback Machine at Archive.org allows you to see much of the web as it existed in history. This is your first and best bet for finding the content. Pro-tip: Use Majestic SEO's historical index to find when the links were acquired, and then choose the date in Archive.org that corresponds with this date. This will help you know the mindset of the linkers if the content changed over time
Warrick: Warrick is a little known tool by the Comp Sci department at Old Dominion that helps you rebuild an entire website by searching through public proxies/mirror caches to find copies of lost content. This is particularly good for rebuilding content that was blocQked by robots.txt. Unfortunately, Warrick is a perl program that may be difficult to operate.



Raised Expectations: Chances are the site for which you are replacing content has greater authority in the industry than does yours. Chances are it is less commercial, more informative, and more trustworthy in general. If you want to acquire a decent return on investment, you need to focus intently on content quality.
Expect to improve upon the content that was created.
Update relevant statistics.
Add new citations and sections.
Consider reaching out to the original author for more information to add credibility.

Outreach

So, you have found your opportunity, created your list of link opportunities, and you are ready to start outreach. Here is how to make the most out of that link list you have.

Contact Finding: There are a growing number of resources for automating the process of contact discovery, although each comes with it's own set of issues.
CitationLabs Contact Finder
Link Research Tools Contact Finder
SEOGadget's Contact Finder
Raven Tools Contact Finder
BuzzStream
Virante's Contact Finder: In Beta

Email Templates: There are many strategies you can employ in the outreach, here are a few of them depending on how transparent you want to be. We find, in general, that if you write good enough content you can be very transparent.
Act as a user who happened upon the broken link
Mix your link in with other valuable, related links
Offer the replacement in a follow up email

Email Templates: Below is an example of a broken link building outreach email. The most important part of the outreach process is that you should tailor your outreach at least to the specific campaign and industry if not to each target specifically. If you can add even a sentence of plausible, relevant customization to each email you send out you will greatly increase your conversion. I promise you if you copy and paste this template you will waste a lot of your opportunities, no matter how good it is.

Source:seomoz.org