Ask your link building client who their main competitors are, and they'll likely name up to five different businesses. Then, ask the same client what keywords they want you to focus on and, interestingly, the competitors for those specific keywords aren't necessarily the same as the company's main competitors.
When researching how a client's competitors acquire backlinks, don't just focus on the company's main competitors. Also focus on the competitors for their keywords.
Take Amazon.com, for example. Amazon.com sells a multitude of different items, so they'd probably list off sites like Buy.com and Overstock as their main competitors. But if Amazon wants to rank highly for a keyword on a specific product, such as books, then their competitors become Borders and Barnes & Noble.
When you start looking at a company's keyword competitor backlinks, see which links the competitors have that you could also get. These opportunities are usually on resource pages, which will also include additional competitors for that keyword.
The Benefits of Providing Value in Link Requests
One useful method that helps me get a better response from webmasters in link requests is by doing a simple task that helps them out. I check the page I want my link on for broken links using Firefox's free Check Page Links plug-in. This will help you in two ways: it helps you get a link on the requested page, and it opens the door to more opportunities.
First, give the webmaster a reason to edit a particular page on their website and, because you've helped them out, they will often return the favor, assuming that you can also successfully convince them that your client's link will be valuable to their readers. One webmaster who recently responded to one of my link requests wrote, "I originally had no intention of doing so, but you went to so much trouble exploring my site - the broken link, and the advice on encoding my email address - that I thought it would be rude or churlish not to."
This technique has helped my clients gain links on high PageRank pages on .edu and .gov sites, simply because the webmasters who maintain these types of resource/library pages don't have the time (or technology) to constantly check on their page's broken links. Many are quite thankful that someone has taken the time to help them improve their site to make it more valuable to visitors.
That's the key to any link request -- it's not about you getting your client's link on that website, but your client's link providing value to that website's visitors. If you can convince a webmaster of your client's link's value, you'll get a much better response rate.
Second, the broken link check gives you websites of competitors that no longer exist, which leads to finding more resource pages, articles, etc., that become new link request opportunities. If you search the missing site's backlinks, generally you can find several quality pages that still link to them. You can e-mail those webmasters as well, saying that they have a broken link, and asking that your link be added in place of the broken one.
Going from one broken link to another can be a rewarding path, one which leads to a lot of valuable links for your clients that not all of the main competitors have.
Free Tools for Competitor Backlink Research
Lots of great paid tools can help you find the best backlinks that your competitors get. But if you're looking for free options, my personal favorite is AlltheWeb.com. Simply search for link:www.yourcompetitor.com to see their backlinks. Adding additional queries, such as site:.edu will help you find more valuable backlinks to your competitors from .edu and .gov sites.
If you use Yahoo Site Explorer, enter your competitor's URL in the "Explore Domain" field, select "Inlinks," and select "Show Inlinks: Except from this domain," so you can see all of the external incoming links. You can also integrate the SEOQuake plug-in for Firefox and sort the backlink results by PageRank, incoming links, and other important metrics.