Adobe Photoshop CS5 is a leading imaging tool used world wide by professionals and amateurs alike for photo manipulation, and computer imagery. The programs is excellent for many uses, including simple things like adding contrast to your pencil drawings, to coloring hand drawn works or drawing entirely within the program itself.

Your basic creation options under Photoshop are the drawings tool, selection tools, colors and filters.
The airbrush tool and pencil tools are the most often used when drawing from scratch.

For advanced creating in Photoshop a  Graphics Tablet (Windows/Mac) (used like a pen instead of your mouse) if desirable. It greatly enhances your work, allow for greater control, smoother lines and faster work than a mouse can offer.

Don't be shy to use filters and plug-ins in Photoshop. These can be used to create some very interesting effects, backgrounds, or make your work seem like it was hand rendered with traditional' mediums.