Since untapered butt joints are tougher to finish, you should try to avoid them. But when you must have them, keep them away from fixtures or daylight which show them up. Bevel the factory edge to give you a slight indent, and double the width of the compound covering the joint (to as much as 2 ft).
Or cheat with back blocks. Install blocks and strapping — recessed 1/8″ from the plane of the joists — where the joint will fall. This forces the butt into a slight recess.
Hang ceilings first, then walls, working top-down. This gives you extra support and a good tight corner where the ceiling and wall meet.
It’s heavy work, so build a brace or rent a panel lifter to support the drywall. Or use your head… literally. It’s not recommended, but if you must, stick a sponge in your hard-hat to avoid headaches.
To speed things up, strap ceiling joists with 1x3s. You can easily shim to ensure level, and you have a nice target for screws. If you want to run wires without drilling, use 2x4s to allow for proper clearance. (Hang drywall parallel to the joists.)
For accurate cuts on openings and outside corners, hang first, then cut — whenever possible.
To cut outside-corner overhangs, score the back (supporting the scrap so it won’t fall). For windows and doors, cut verticals with a drywall saw, then horizontals. If there’s a door opening, you can score from behind.
To cut outlet holes, rub the face of the box with chalk or lipstick. Position the drywall, hit it with your palm, then take it down and cut with a drywall saw. Or mark the coordinates on the floor, hang the drywall, then measure up and cut it in place.