Your blog/site starts to get a bit of traffic and a few regular readers, so the opportunity will come along to accept or provide links for your site.  The idea behind links can be two-fold.

Firstly you are looking to obtain links that will pass ‘link juice’ to the site and strengthen the PR of the site, thus helping to stabilize and improve rankings within SERPs.

Secondly you are looking to gain links that may attract visits, so you may find relevant sites that are within same industry/sector, where people interested in your topic may decide to visit your site.

The most important thing to remember when linking is to make sure you get a nice varied portfolio of links, remember natural link building is the way forward.