Backlinks can be found in many places across the internet.  These opportunities come in many forms such as the likes of social media sites, guest blogging opportunities, directories, blog comments.  Generally, to increase the power of your links for Google it is wise to create links that can enrich the experience of a user to your site with original content.  These can be created by meaningful responses to comments, replies or original posts in forums, or a blog created on another site for anything pertaining to your industry.  It is best to be informative and educational.