10-04-2009, 07:15 PM
The only tip I can give you is to break down your workflow; first fix your values and lighting in grayscale. Once this is solid move along to color and experiment with different layer modes.
Another tip I can give you is to study Color Theory, so you know what you're doing when applying color. It also gives you more confidence in working with a color wheel and teaches you about color temperature and harmonies. I recently finished studying color theory and it was the best thing I ever did!
The book I used was 'Color' by Betty Edwards; ISBN 1-58542-219-3
Best of luck and have fun!