Write nice content that people would like to link to or offer a service for free ... And then post it to a few social bookmarking sites so other people can get to look at it and write something nice on their own blog ....
Directory submsiion, social bookmarking, link exchange, buy links are very effective ways to build back links.
Let me give you an easy jump start. Go to the following link and start submitting your sites and at the end of 2/3 days you will have an easy 500+ linkss. http://therateuwant.com/Article/22/600_FREE_Web_Directories_To_Submit_Your_Web_Site
but you won't be able to see all the "low links" from free directories. just check it with backlinkwatch, etc.
Try posting more on forums and link exchange with related sites, directory and article submissions also helps in your campaign...
Please follow the procedure 1.Directory Submission 2.Article Submission 3.Social Bookmarking 4.rss Submission 5.Forums Signature 6.Forums Posting. 7.Tagging. 8.blog posting
Stick a link in your sig on one or more forums (Preferably with a decent PR to ensure they are spidered well), and post regularly. On the side of that, submit to free directories everday. It should only take an hour or so to do 100. Use SEO Elite, or manually track down potential link partners and webmasters of relevant sites and email them. If you spent about 4 hours everyday on the above 3 steps you would be looking at 2000 - 4000 backlinks a month maybe?
you wants to do directory submission, article submission, blogs submission, social bookmarking and others basic steps
I would go for link exchanges, especially with sites of your niche (Google loves related sites links) and with paid links (again on the same niche: be aware that if you get busted by Google...)