I started out on my own: reading books and visiting galleries and museums. I find that looking at lots and lots of real prints, framed and on the wall, really helps me because a framed print is really what I want to end up with. I still read a lot, and visit any photography and art exhibits I can find. I collect photography books almost as compulsively as I collect cameras.
As I became more interested in photography I started taking classes at the local community colleges, university, and art center. I still try to take at least one photography or art class/workshop a year, and I occasionally teach photography at the local arts center.
I worked in a professional photo lab for almost 4 years. Talking to amateur and pro photogs all day every day probably taught me more than anything.
Read a lot, look a lot, and talk to other photogs. That's how to learn.