Your mother would be the first place to start, I'd gather as much information from her and your known family as you can. Ancestry.com could be useful, any of the social medias, and people finder, especially if you have his name.
Does anyone know how to go about trying to find someone. I'm trying to find my biological father and I have no idea where to start?
Have you tried www.spokeo.com?
That depends on how much info you have on him. If you have his name you can start by searching Facebook. If you have his name and now where he was born you can look for people with the same last name in his hometown. They maybe related and can help. Your birth certificate should have both his name and birthplace listed.