Google is the world's number one search engine, and currently provides the results for around 80% of all the searches done in the world. Because of that, it is vitally important for any website that relies on search engine traffic to do well in Google. Doing well in Google means making the site 'important' in Google's eyes and, to do that, the site must have good inbound links - as many of them as possible, and preferably from important pages (pages with medium to high PageRank values).
How do we get inbound links?
There are a number of ways. Some of them are:-
Link exchange centers
Find a join free link exchange center like LinkPartners.com . There you can find a categorized directory of websites that also want to exchange links. Be careful not to sign up with FFA (Free For All) sites because they are mostly email address gatherers and you can expect a sudden increase in email spam soon after you sign up. Also, only sign up with centers where you can approach other sites personally, and where they can approach you personally.