Keep it simple. "Thank you" is a perfectly acceptable response to someone saying they like your drawing style, singing voice or turn of phrase. "Thank you very much" is also OK, but you probably want to keep the effusive gratitude to a minimum, no use looking desperate.
Resist the temptation to downplay the complement. After all, the giver thinks highly enough to comment on your efforts; by saying "Oh, it's nothing" or "You liked it? Man, I thought it was horrible" or "It's my least favorite piece in the show" you're telling your fan that a) he doesn't know what he's talking about or b) she has bad taste. That's not what you want to do, so cut out the false modesty.
Give extra information only if the praise is paired with a question. Many people pay very honest, simple compliments as a way of acknowledging your effort and thanking you for your performance. This also stands in the place of a goodbye for many, so it would be absolutely horrifying to then be trapped in a conversation with an artist who rambles on.
Be aware of your body language when interacting with people. Crossed arms close you off visually and may quietly advise would-be appreciators to steer clear instead of approaching. Make eye contact with people as they pass (but don't stare) and try to keep a pleasant expression on your face, even if nerves prevent you from actually smiling.
Make notes on the features you are complimented on the most. Not only will this give you an idea of what is working, but also what you might want to spend more time developing in the future.