Great question. For some great answers check out Jon Schindehette's Art Order Blog. He has some of the best illustrators and Art Directors in the scene giving great advice. Not just for doing covers but for being a great artist.
"I recently received a question as part of the Ask the Art Director portion of ArtOrder, and thought it was a nice industry-wide question. Due to the nature of the question, I sprinkled my list of AD's with some cover artists that I've had the opportunity to work with.
And here's the question:
"I'm a recent graduate from the Academy of Art University in San Francisco in illustration. My dream is to do fantasy book covers. I have really focused my portfolio on that and I know I have everything it takes to be a great freelance cover artist, but now I can't seem to get my foot in the door.
I was sure all I needed was a rep, but I've had no responses from any. By the looks of it, 99% of the artists I see being represented are doing graphic and cartoony stuff which I will never be able to do. The reps are only interested in art that is viable for advertising is how it seems.
So my question is--how do I meet the right people? How do I get my art seen? Do I need to start at a publisher smaller than Wizards or Tor? If so, how do I find them? Are the conventions really a good way to get started?
Check out my site if you have time to see what I have to offer."
I left the artists name and url out of the email on purpose. While they agreed to ask their question in public, I wanted to allow them the option of reading the critiques in private.
And the answer is..." click here for the responses