If you're grip is a little strong you will have a small cup.
The easiest thing to do is to take your grip and take your backswing to the top or end. Then, using a mirror, make sure that the face of the club (driver is easiest to tell usually) is PARALLEL to your LEFT FOREARM.
If you go to
http://redgoat.smugmug.com , brady riggs site, he has a grip fundamental section up now that shows the differences in grip type and flat/cupped positions.