Preparation--Before starting there are several things you must consider. One is drywall thickness-Drywall comes in a wide variety of types and thickness,if redoing a whole room or wall 1/2" regular should be fine.
Anything else such as areas that will be wet, exposed to the outdoors, fire protection etc you will need a specialized wallboard.
See the U.S Gypsum website for a complete listing and description of the various wallboards that are available.

Your next consideration is weather to hang vertically or horizontally. Horizontal applications are generally preferred because they usually minimize joints. The general rule of thumb is to use the longest length panel available and offset all end joints in adjacent rows. A horizontal application using 12' long panels is a safe bet for most walls. If you have ceilings that are 8' or less,you might consider standing upright,8' boards. This is nice as it eliminates "butt" joints the untapered edge of the wallboard.
Use the drywall calculator to figure the amount of board you need.

Here's what you need for a basic drywall installation:

• Screw gun or electric drill with special bit if you are going to use drywall screws.
• If you're using drywall nails, a drywall hammer is preferred over a traditional claw hammer.
• Caulk gun (if you'll be using panel adhesive)
• Utility knife and extra blades
• Metal tape measure
• Marking pencil (not too sharp!)
• Keyhole saw, sabre saw or drywall plunge-typerouter
• Tin snips or hack saw
• Step ladder
• "T" square is very handy for cutting