If you are looking to get quality backlinks, try the following:
1. Ask if you can guest post on the blogs of others -- only if the blog is related to your niche, however. It's also best if the site gets a decent amount of traffic and has a decent pagerank itself.
2. Post articles on sites like Ezines, then link to your website. Make sure that these articles are interesting, informative, unique, etc.
3. You can build mini-sites or mini-blogs around the Web to use as backlinks.
4. Use forum posting to your advantage. Not only will good forums sometimes serve as great backlinks, but they can also provide you with more natural traffic as well, especially if your posts are interesting and helpful.
5. Ask if you can trade links with other sites and blogs that you like. Make sure that these sites aren't penalized by Google for anything.
6. Leave comments on blogs. Be careful with this, however, because a lot of people have used this as a method of spam. Don't spam; instead, leave helpful, relevant comments on blog posts that you actually like.