For this you must have to do following off page techniques to get the back links to your site.
Directory Submission,
Social Bookmarking,
Article Submission,
Blog Posting,
Blog Commenting &
Forum Posting.
Well besides these there are some other activities from which you are getting the traffic to your site.
Classifieds Submission,
Press Release Submission,
Search Engine Submission,
RSS Submission,
Ping Services etc.
Nowadays the latest technique to get the back link to the site is Link Wheel & Wiki Links. You can also try for these.