Leave a 1/8-in. Gap
There's no reason to measure and cut drywall for an exact fit. It'll usually just cause trouble. Jamming in a piece that's too tight will crumble the edge or break out a corner (left). And removing a piece to shave a too-tight edge is messy and time consuming. A loose fit avoids this problem. Cut it to leave about a 1/8-in. gap at edges (right). In fact, when you're hanging the ceiling, keep in mind that 1/2 in. along the perimeter will be covered by drywall on the walls. And the same is true of inside wall corners. So you can safely cut these pieces 1/4 in. less than the actual measurement and leave a gap in the corner if necessary. Even a piece whose edges aren't covered should be cut a little short. It's easier to fill a 1/8-in. gap with setting-type compound than to cut and repair a broken edge or corner.
Taping drywall is time consuming and tedious enough without adding extra joints, especially those hard-to-tape butt joints (top). So plan your job to use the longest and largest sheets possible. And don't scrimp on materials. Drywall is cheap.
If the walls you're planning to drywall are between 8 ft. 1 in. and 9 ft. 1 in. tall, consider ordering special 54-in.-wide sheets of drywall to avoid an extra horizontal joint. You'll find 54-in.-wide drywall at drywall suppliers, or you can special-order it from most home centers and lumberyards. You'll also speed up your job by using 12-ft.-long sheets of drywall rather than standard 8-footers (bottom). However, hauling 12-ft. sheets is difficult and getting them into the house can be challenging. For large jobs, have the drywall delivered. Many drywall suppliers will even stack the drywall in the house for an extra fee.
Avoid Future Cracks
Avoid lining up a sheet of drywall with the edge of a door or window opening (left). Your home tends to shift and settle slightly, and that movement shows up at the corners of windows and doors. A joint at this location, even if it's well taped, is weaker than solid drywall. Chances are it'll crack in the future.
It's better to notch drywall around openings rather than to make a joint. For interior walls, simply continue over the opening with a full sheet and cut out the opening after you fasten the sheet (right). Windows on exterior walls are a little trickier. Measure and notch the sheet before hanging it. Get help when hanging notched sheets because the skinny section above the opening is often fragile. It's OK to join sheets over an opening (and often easier if you're working alone) as long as the joint isn't in line with either side.
Watch this video on how to cut drywall before you begin your project.