Outside corners tend to take a beating, so it is a good idea to reinforce them with a metal corner bead. This is nailed to the outside corner, and then joint compound is applied. Keep in mind that you should allow a day for drying for each coat of joint compound on corner joints. Pick a time to tackle this project when you won't mind having a wall "under construction" for a few days.
This guide outlines the procedures for applying drywall, cutting and securing the corner bead and applying drywall compound.
APPLY DRYWALL TO CORNERS
Apply drywall over one side of the corner then the other, using adhesive and screws.
MEASURE AND CUT METAL STRIP
Measure the length of the corner, and cut the bead to length with a pair of tin snips. The metal is thin and easy to cut. Cut from one edge toward the bead in the center and then cut from the other edge toward the center.
NAIL THE BEAD TO THE WALL
Drywall bead is nailed to the wall instead of screwed in because the screws tend to bend the metal. Drive a 1½-inch drywall nail every 9 inches into the holes along the edge of the bead.
APPLY DRYWALL COMPOUND TO THE BEAD
Dip the knife in drywall compound and pick up about an inch of compound. Rest one edge of the knife against the wall and the other against the bead. Pull the knife along the bed to apply the compound. Repeat on the other side of the corner.
LET THE FIRST COAT DRY OVERNIGHT AND APPLY SECOND COAT
Let the first coast dry overnight and apply the second coat exactly the same way as the first, using a 10-inch knife.
APPLY THIRD COAT
Using a 12-inch knife, apply the third coat like the second.