If you are coming to racquetball from another racquet sport that uses a longer racquet, you may need to adjust your expectations about the correct racquetball grip.
In racquetball, you need to hold the racquet so that your hand extends below the end of the grip. The little finger should be entirely below the grip. While this may seem bizarre, and a likely way to lose control over the racquet head, there is a good reason for using this grip in racquetball: The racquet is just too short! By holding the racquetball racquet lower down than is usual in most racquet sports, you effectively lengthen the racquet and gain pace on your shots.
Also, good racquetball players use a lot of wrist snap when contacting the ball. This extended grip allows unimpeded movement of the wrist throughout the full range of its natural motion. (The butt of the handle can't bump against your wrist if it's touching the base of your palm.)
To take the proper grip, hold the racquet, by its throat, in your non-hitting hand so that the face of the racquet is perpendicular to the floor. Then shake hands with your racquet so that the base of the V formed by your thumb and first finger is right in the center of the grip. Now, slide your hand down the grip so that your little finger no longer contacts the grip, and so that the base of the grip is against your lower palm. This will give you a grip that can work for both forehand and backhand. (You may want to make adjustments during play by moving the V just to the right or left of center).
Make sure that your little finger extends all the way below the base of the grip. Since there may be some shifting of the grip during play, and the base of the grip may rub against your palm, wear a racquetball glove to avoid blisters.
