One-Handed Backhand
The traditional grip for the one-handed backhand is the Eastern grip. With this grip, a right-handed player’s wrist should be slightly to the left of the top of the racket handle when looking down on the racket, with the racket edges perpendicular to the court. A left-handed player’s wrist will be slightly to the right of the top. Think of your thumb as having a top, bottom, outside, and inside. The inside part of the thumb should be in contact with the back flat bevel of the racket handle. You can align your thumb in various positions along that part of the grip, but it is essential that the inside part be in contact with the racket. During a point, the thumb’s position may change, but the part of the thumb that touches the grip should not.
Tennis: Steps to Success Jim Brown,Camille Soulier