measure & make a mark on the (wood) stud to the top of a panel, then measure down to where the bottom would be, hammer a nail in at the mark and set the panel on the nail to support it while you fix it to the stud with drywall screws. Use a level to set the depth of the panel (most torpedo levels are exactly 5/8" thick- same as a sheet of drywall) For steel stud a long tek screw will give the same result as a nail in wood but it is a bit trickier.
PS I was surprised to learn that 2 guys I work with who each have 20+ years experience in the trade never once took out their tape measure to discover that a torpedo level is 5/8" thick!
