And if you need to, try a different program. Nowadays there are many ways to get great results. SAI, Manga Studio 5 and Painter are all cheaper than Photoshop. Some programs are better suited for artists with a traditional background (like SAI), others are more technical and rely on coming up with creative uses for tools (like Photoshop). Look at lots of tutorials, find some art you admire and try to replicate the results using your own knowledge of the tools. Out of that will come your own style and approaches. And don't forget the fundamentals...study up on color theory, lighting, that sort of thing. I'm certainly no expert, but that's what I try to focus on every time I color something.
There are mountains of coloring tutorials out there. I taught myself my method by studying cartoons/anime, reading up on cel shading, and I bought a couple of books. "Hi-Fi Color For Comics" (I'm pretty sure that's the title) is a good one.
I've been promising folks a tutorial of my own for a long time but I don't know if I have it in me to make one. I'm lazy.