Ideally, you should be linked from every high-traffic site that is of interest to your target market. Develop a strategy to find all of these sites and arrange links.
Start with the popular search engines. Most people use search engines and directories to find subjects of interest on the Internet. Most of the people searching never go beyond the first 10 to 20 results that the search engine returns. Thus,
these top 10 to 20 sites get a lot of traffic. Search your most relevant keywords in all the popular search engines and directories, and investigate these top sites for link possibilities. Some of these sites will be competitors and might not
want to reciprocate links. The best opportunity for links is with noncompeting sites that have the same target market. I suggest you take your most important keywords, do a keyword search in the 20 most popular search engines and directories, and review the top 30 sites in each for potential link sites.
Another strategy to find useful link sites is to see where the leaders in your industry and your competitors are linked. I use the term competitors very loosely. It would include your direct competitors, your industry leaders, companies selling noncompeting products to your target market, companies selling similar types of products or services to your target market, and companies that compete with you for search engine ranking. See what your competition is doing. Determine where they are linked from, and decide whether these are sites that you should also be linked from. Learn what they are doing well, and also learn from their mistakes. You should be linked everywhere your competition is appropriately linked, and then some.