Each link pointed to one specific page is considered as a vote for that page and will affect its page rank. Anchor text of a link or in case of images the ALT tag would tell both Google and visitors what that page is all about that will help with the search engine ranking of that page for its specific keywords.

The relevancy of a page linking to your own page is also important. A link from a page with too many outbound links is not very useful so just don't waste your time submitting your site to web directories or leaving comments on do-follow blogs.

There are many different methods of link building including article and press release distribution, link exchange, finding high quality sites to place your link on, just to name a few.