I'm currently using program called PhotoExpress 2.0 - don't laugh it came with the computer.:D
Though there are definatly better programs around, my advice is (if you have not had much drawing/design experiance) to start out by sketching on paper 2D drawings etc... then start on 3D sketches - the more practice the better, photoshop programs should come after you are confident that you're quite good with just sketching.
Sculpture experiance will also help.
I'd suggest you visit
www.cardesignnews.com and get some more valuable info from there.
If you have contacts in the industry then use them, I was fortunate to get some feed back from the late Geoff Lawson about five years ago which was quite helpful.