By just commenting on Do follow blogs you can start to build backlinks to your site. When you comment on relevant DoFollow blog, your SERPs will increase.

DOFollow blogs are blogs that give you a backlink just for commenting at them.

You can search do follow blogs related to your site/blog using,
http://www.backlinkspot.com

The more comments you do, the more backlinks you’ll get.
Remember not to do spam comments! If you do comment spam your comment will be deleted by the blog owner. Try to add a value to the blog post with your comment!

All the best for your link building campaign.