For small openings like an outlet or switch box, you will need to use a small saw or a jig saw to make the cut. This is usually a quick and easy job because drywall is a pretty soft material. Be careful to make close measurements before making any cuts because you can not glue this stuff back together. It will cause additional waste or more seams to hide. Neither of these are good.
Continue the installations and cuts until the job is complete. If you have to install a ceiling, always put the ceiling in first. This way, the edges of the ceiling will rest on the walls. It just makes the job go easier.
You will need to get your tape and mud ready to go. Using your 6 inch or bigger knife, spread a thin layer of cement along a seam. Now, reload your knife. Cover the seam with the tape. Use your knife to put another layer of cement over the tape. Try to feather the edges as much as possible, but do not get to particular at this point. Get enough cement to get everything covered along the seam and several inches on each side of it.
Mud and tape every seam. Now, you need to go back and cover every screw head with cement. The screws should be driven in far enough to be countersunk into the surface of the drywall. This will mean that you have a little depression to fill with mud. When you are finished, you should see a lot of one inch circles all over the wall.
Now, you are ready for the final steps. You will need to carefully sand all of the drywall cement once it has completely dried. The goal is to smooth it so that it disappears when you paint it or cover it. You will need to feel with your hands and stand to one side and look at it carefully to tell how this is going. If you are having problems making it look right, you may need to put on more cement and widen the seam covering even to a foot or more. A wider seam is easier to blend than a narrow one. It is a good idea to let the cement harden about a day before sanding it or sanding it again.
When you are satisfied that you have a good taping job, it is time to put away the drywall tools and get out the painting supplies. Should you see that you have left a seam a little too noticeable, you can always wait on the paint to dry and sand the paint away. You can then make the decision about whether the seam just needed a little more sanding, or you may decide it needs a wider spread on the cement. Either way, it can be done over after a coat of paint if you have to do it that way.
