Top 15 ways to build backlinks

Here it is, the list! If you follow these methods you should have a large quantity of good backlinks pointing to your site.

Submit site to directories. These are basically giant catalogues of web sites and, in many cases, offer high quality free backlinks. One of the best is the Open Directory Project.
Article writing and submitting. You submit articles to article directories like these and they let you put your link at the bottom. This means your link is surrounded by keywords giving it more weight.
Forums signatures. If you take part in forums, especially those related to your site, post a link in your signature. If you are respected on these forums, or post a helpful nugget of information, then people will click on these links.
Blog posts. If you are blogging then always include a link back to your site. You can also interlink all your sites, especially if they are liked by the search engines. Some blogs also like a guest blogger - you could write and article and you'll get a free backlink from the site's owner in return.
Link exchange. Aah! Ye olde link exchange. Used from the dawn of the Internet, you mail a site owner to see if you can exchange links with him. You post a link to him on your site, and he reciprocates this. Easy!
Reviews. Ask for reviews of your website and you'll get a backlink from the reviewer.
Contribute/create something for free. Anyone who uses this will see your link. These people already like you so they may click on it.
Create a top 10 list. Top 10/15/50/100 lists are great pieces of linkbait. They will draw links from lots of sites if people know about them.
Run a contest. If you run a contest on your site this will also attract plenty of backlinks.
Host a collection of free tools. If, on your site, you have a ton of useful tools, then share them! These will attract links like there's no tomorrow.
Interview experts. Try and get some interviews from experts in your niche. Chances are they will link to your interview and this will also drag in links.
Get interviewed. On the flipside of number 11, if you know a lot about something, get interviewed about it. They'll let you have a link for your trouble so it's worth it.
Social networking. Create a group on Facebook or MySpace. Not only will you get a link, but loads of people will see the page and click on it.
Create quizzes. Again, just like top 10 lists, they are great for linkbait.
Make an offer to buy Microsoft! If it breaks through the news, you'll get a LOT of traffic to your site. Beware though, this could land you in court if you don't check it VERY carefully beforehand.

Good luck with these tried and tested techniques to get ranked highly by Google and other search engines.