First thing why make friends? You make friends to expand your reach and audience to grow and understand yourself. People have different profession. Friends helps each other to remove the difficulty according to their profession.
Making social friend. There are many social sites you can use to make friends. Mostly, Facebook, Twitter are most commonly used social website. Depending on your location, social sites exist for region base.
How to expand your reach? Share to the world what things you like and post about the things which you are interested in. People know you as the profession you do and they know it well as you post it on the social site.
I use Twitter to post the things that interest me.