[dennis_vartan]

Learning Photoshop mechanics and UX concepts isn't sufficient, IMO. One can be proficient in $DRAWING_TOOL and still unable to compose something that looks good. As much as I appreciate sites like Tutsplus, they teach mechanics but rarely answer the "why." Why do we add this 28% opaque drop shadow in step 37? Knowing why something looks good is essential to being able to create new works.

Two books I personally found very useful for "why," both discovered via HN:

   "The Non-Designer's Design Book"
   "Design for Hackers"

[seanmcdirmid]

Well, you also have to learn Illustrator, which is probably more important than photoshop these days.

Knowing what looks good requires lots of experience. Just learn the tools and get started, you'll suck at the beginning anyways.