After all the drywall is up, the next step is to apply corner bead. The bead serves two purposes: It protects the corner from impacts, and it provides a guide for your knife as you apply joint compound to the corner. You won't need bead in corners that will receive molding because the molding provides protection and joint compound won't be used on those corners.
There are two styles of bead: standard, which makes a crisp, square corner; and rounded, which makes a soft, smooth corner. Both are available in white vinyl and galvanized steel. Both materials work well, so choose based on price and availability.
For an arched passageway or other curve, apply flexible bead. It is similar to standard corner bead but has cuts across the flanges at regular intervals, allowing it to bend around a curve.
Whichever type of bead you use, it is better to attach the flanges with drywall nails than with screws, which tend to make the bead pucker. Use nails that penetrate studs or other framing at least 3/4 inch.
When a raw drywall edge meets a dissimilar surface, such as wood, it is nearly impossible to get a clean fit. Two products create a crisp edge in this situation:
J-bead is nailed into the wall before the drywall is installed. Prepaint it because it remains visible when the job is finished. (Spray paint works well.) J-bead is particularly useful where condensation might wick into the drywall. It encases the drywall, isolating it from the abutting material.
L-bead is nailed to the face of the drywall. It is covered with joint compound (as corner bead is) after installation and painted with the rest of the wall. This bead does not extend over the back of the sheet.