Backlinks contributes a lot to your pagerank. More the sites linking to you (backlink) , more is your pagerank. And more famous the site linking to you,the more credit you get. Backlinks in other sense increases the
visibility of your site on web, which is the actual reason for higher
pagerank. So here are some points how you can increase your backlinking :

->Dont forget to comment on each and every blog you visit (Do not spam).
What i mean is, write some good things about that blog (not your blog),
and include your URL over there.

->Participate in forums, include your URL whenever you post an entry.

->Linking within your sites, for eg. if you have 3 pages on your blog/site, add a link to 2nd page from 1st page, add a link to 3rd page from 2nd page, and from 3rd to first. If you are using a blog then each post will act as a new page, so what you can do is link the main keywords of the site to the main page eg. for Make money online add <a href="http://www.cool-blogger.com">Make money online</a> to the blogpost.

->You can do what is "Link Exchange" with other blogs. This simply means
you put his URL on your blog and he puts your URL on his blog. If you
dont want it to appear to your visitors (anyways other person wont get
loads of visitors from your site to his through this link) just use the
link name as . (dot) eg.
<a href="http://www.cool-blogger.com">.</a> will look like
. . Human eyes wont read it, but search engine crawlers will!

->Whenever you join any community or a social bookmarking site dont forget to add your site in your profile.

->Submit your site to all free directories available on web.

Here are some tools which will help you to keep an eye on no of backlinks :

Seopro.com.au

Submitedge.com

Rankalert.net

Smartpagerank.com

Here is a link to submit your site to top search engines/directories :

Addme

Related Sites :
Link-building-bible