Link building a challenge for every webmaster or site owner. You can do following steps to build free backlinks.
(1)Social Bookmarking
-Make sure sites are no-follow
(2)Forum Signatures
-Easy and best way to build quality back links. You will get huge traffic also. Make sure to use do-follow link forums.
(3)Blog Commenting.
-Make sure do-follow
(4)Article submission
(5)Directory Listing
(6)Social networking sites
(7) Link exchange
-Beware of link farms.
Those tips are great. SEO and link building has a strong relationship. More links mean more SE traffic.
I personally prefer Forum participation and Blog commenting.
One technique I use is to set up a Google Alert for my targeted keywords. Then every morning I get an email about the blogs using that keyword. I can then comment on the blog as it is relevant to my niche.