The two-handed backhand has become the norm these days.
It is much easier to hit a two-handed backhand than a one-handed backhand when a player first learns how to play. It also results in a stronger shot for most players. The majority of tennis professionals will start players with two hands because of this.
It is important to remember that your off hand (non-dominant hand) should be doing the same thing on your backhand that your dominant hand does on your forehand. A right-hander should think of hitting their backhand with a left-handed forehand swing, using their right hand to help (the opposite for a left-hander).
The players with the best two-handed backhands can hit a one-handed forehand off of their backhand side very well (Andy Murray, Sloane Stephens, for instance). Your dominant hand and arm will want to take over on the two-handed backhand but work on emphasizing the off hand during the swing. This will allow you to execute a mirror image of your forehand, resulting in a more consistent and powerful swing.
Steve Annacone, USPTA Elite Pro, is the Director of Annacone Tennis, www.annaconetennis.com and MyHamptonsPro, www.myhamptonspro.com in East Hampton, NY . Steve is also a tennis professional at Ventana Golf and Country Club in Tucson, AZ. In addition, Steve and Miguel Coelho have introduced the JET (Junior Elite Tennis) program at the Tucson Jewish Community Center for high level players ages 8-18. Please contact Steve at email@example.com