Ensure that all fixings, screws or nails are seated below the surface of the plasterboard.
Fill any areas greater than 2mm deep with a setting compound such as Gib Tradeset and leave to dry.
Using a 150mm broad knife, fill the recess formed by the edges of the sheets with jointing compound.
Centre the paper tape along the joint and using a 150mm broadknife press the tape down into the compound.
Draw the broad knife, held at about 45
Apply a finishing coat of compound with a 280mm trowel.
Joint edges should be feathered at least 50mm beyond the edges of the previous coat. Allow to dry for about 24 hours. Lightly sand in the same direction as the joint using 220 grit, or finer, sandpaper.
After sanding, mark any defects and imperfections with a pencil, then retouch these areas with compound. Leave to dry and sand. Repeat this process until the desired finish is achieved.
Poor fixing of plasterboard will make achieving a good finish difficult.
Stopping can hide small mistakes but cannot make poor fixing look good.