Measure from one end of the wall to 8 feet. Draw the tape measure back to the center of the edge of the last stud within the 8-foot span.
Transfer the measurement to a piece of wetrock. Mark a straight line with your pencil, running it alongside the level. Cut on the line with your utility knife, going 1/8 inch or so into the surface. Snap the piece at the cut line.
Press the piece to the wall so the cut end is facing the corner. The other end should run vertically along the middle of the width of the last stud. Secure the sheet with galvanized screws, driving them in every 8 inches along each stud.
Repeat the process for each sheet of wetrock, working your way up the wall and covering the whole surface. Position the boards so different courses line up on different studs, "staggering" the boards. Use a jigsaw to cut around bath or shower fixtures or any other obstructions.
Set drywall tape over the seams. Spread joint compound over the tape, using a drywall knife and making the line of compound just wide enough to cover the tape. Get it flat and smooth. Spread more compound over each screw hole. Let it dry for six hours.
Apply another layer of joint compound to the seams, widening the lines a little. Let this layer dry for six hours as well.
Spread on a third coat of joint compound, making the seams wider than before. Let it dry. Sand it smooth with a drywall sander. The wall is now ready for painting.