First of all: Patience…
I can sense from the way you posted (I had tried using other 3D software like 3DMax, Maya, Bryce, etc) that you expect to have instant results…
Learning any 3d app requires a lot of time and hard work, at least one year for a little advance, at most all your life to have great results, yet it’s really worth the effort.
Polymodeling apps (maya, 3ds max, xsi) will help you a lot in creating any kind of content combining them with zbrush Dont leave them. Photoshop also is a must.
Second: Observation
Learn about anatomy… it will improve greatly your sculpts.
Observation, will help you know how things are. Otherwise you will might be unable to sculpt or model.
Learn how the light and materials interact, and react… will be the final output of your work (rendering)
Third: Passion
Don’t get upset if your first works are not how you’ve imagined them… eventually you will become a better artist. But if you abandon this, sureley you will NEVER be an artist at all. Search for crits, not only here at zbc (a great place to start), but in every place suited to that.
Good luck!