All you keep hearing is link exchange, trade this link, do that, and build links. Well, the truth be told is that it's all about the relevance, quality, and how the link is show on the site. It really does not matter if Millions over night basic sites link to you this kind of action could easily get you banned from google or if not banned really hurt your chances.
What the Search Engines are looking for is a normal way of your site growing popularity and other sites finding your and thinking it's a positive resource and will link to your site.
Here is the complete truth being told about linking:
1. If you are a lasik eye site and another lasik surgery site links to you, this will add a positive boost because of the relevance of the sites. Now for example i you have a basketball site and soccer site links to yours...more or less it's not as relvant and not as good as having link from the same topic.
2. Let's say your site is all about window blinds and the link to your site is like this window blinds that will give you a boost because the link is a search term.
3. This is a must and g is really cracking down hard on this one. But, your site popularity or links need to come at a slow steady natural pace. Compared to the overnight wondering of getting tons of links.
4. Lastly, if you can pull of a link to internal pages of your site, as well as your home page, this is like a huge bonus that willl give your site deepth and looking deep.