I just read an article at SEO Traffic Spider about the strategy of building backlinks for your website.  The article does a good job of identifying the difference between legitimate and illegitimate practices of acquiring external links to your website. 

The practice of getting other sites to llink to your website is the cornerstone of what is known as "Off-Page SEO" and, some argue, contributes to upwards of 75% of where your site will rank in the search engine results pages (SERP's).

The aforementioned article talks about ways of developing links in very general terms and lists ideas such as directory submissions and creating quality content.  I personally like to offer more concrete ideas. 

As such, one piece of advice that I would offer for obtaining quality backlinks to your website is to do a search on Google to see who is linking to your competitors' sites.  This can be done by typing - link:competitordomain.com - into the search field on Google (no spaces).  By looking through the list of sites that are linking to your competitors with similar content, you can find some websites (ideally .org, .edu and .gov) that might also be willing to link to your site if you have quality content for them to link to.

If you want more specific information on any of the ideas in this list, let me know.

What other ways have you found to effectively acquire links to your website?