One of our viewers sent in this tip.
Mark the wall where you want a curtain bracket.
Cut a piece of wide masking tape perfectly square and tape it to the table.
Place the curtain bracket into the corner of the masking tape and use a pencil to mark the screw holes on the masking tape. Now fix the tape to the wall where you want the curtain bracket.
Drill your screw holes right through the tape.
They will both be in the right place.