Check the Fit Before Fastening
Even with careful measuring, you'll often run into an outlet hole that doesn't quite fit. The common mistake is to screw the drywall to the framing before trimming the opening. Then the drywall will break around the electrical box (left), requiring extra time to patch. The key to solve this problem is to check the fit before you press the drywall tight to the wall.
After carefully measuring and cutting out the openings in your sheet of drywall, hold the drywall in place. If the fit is close, fasten the sheet with a few screws along the top edge or well away from the outlet openings. Trim excess drywall away along tight box edges with a utility knife (top right) until the drywall slides easily over the outlet boxes (bottom right). Then finish fastening the drywall.
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.