Five rules to taking pictures for the cover

Rule One No cluttered background
Rule Two Make sure you focus on the lead singer if it is a band shot so you know who they are - If it is a singel artist make sure it is a medium shot or a close up.
Rule Three Leave room for a masthead and don't cut heads off!
Rule Four No high angle shots, fine for double page spread.
Rule Five Animate your band, make sure they're doing something and looking at the camera.