Your capability in tennis begins and ends with the grip. This controls the way you volley, return serve and it gives you your spin. When practicing your forehand, you also need to practice your grip. Sloppy technique here may result in a problem throughout the rest of your game. Now, there are a few different forehand grip techniques to consider, each of which come with some advantages and disadvantages. While there's no reason you can't master all of these grip types, it's best to focus on one and go on from there.
The eastern forehand grip
This is probably the grip you already know and the grip you were first taught (if you've had a teacher work with you before). With this grip, you take the palm of your hand and place it on the side plane of your handle, holding it parallel to the racquet face. Your index finger knuckle rests on the base of the plane, giving you the sturdy swing you desire. The grip is straightforward and makes it easier to learn other techniques in tennis. However, you'll never maximize your topspin with this grip, so consider looking into some of the other options.
With this grip, take your plane and place it on the lower right slant of the racket. This gives the racket a bit of a downward tilt. While doing so, the racket will strike the ball in a more forward position, which produces more topspin. You will need to swing up more at the ball, but the top spin is desirable. Keep in mind that this grip isn't the best for striking lower hit balls.
With this grip, place your palm on the bottom plane of the racket's handle. This forces the racquet face to tilt extremely downward. You do need to strike the ball in a much more forward position, although it offers the highest level of topspin. It is great for higher level balls but difficult for low-level balls, so keep this in mind. If you want the highest level of topspin, go with this grip.
There are a few options available to you when it comes to your tennis forehand grip. Stick with one when starting off, then once you are comfortable with the initial grip, you can experiment with others to see which you like the best and which offers you the best potential with your tennis forehand.