There are many different grips that can be used, depending entirely on playing style. The most common grip is the Eastern grip, the balls gets less spin but better distance. This is a good approach to use for beginner players.
Then there are grips that the more professional players have, such as those who play at the elite level. Most international players use grips such as the Semi-Western-grip because it gets a lot of spin (topspin) and provides better control.
When doing a serve, volley or smash the Continental grip or hammer grip is advised. It is simply the same grip as when holding a hammer.
First begin by standing in the starting position. Then when the ball comes, pull back the racket as you take a step forward with the left foot (right if you are left-handed). In such a way that when you meet the ball you have the racket in front of the body. The swing must come all the way up from your left shoulder.
A backhand is very similar in technique as the forehand. You must Pull back the racket while moving forward with the right foot (left if you are left-handed). Then hit when in front of the ball. And make sure the swing follows all the way through
The important thing is to have the racket in front of your body, preferably at head height. Legs well spread. When the ball comes flying towards you move the racquet towards the ball (no forehand swing) and hit the ball in front of the body. While doing the shot you should move one step forward. Regarding the backhand volley, go forward with the right foot (just as with the base hit).
You mostly use the continental grip for serve and volley. It is sometimes called the hammer grip. When you serve you should stand diagonally across the line (it can be different). You throw the ball up a little in front of you, while taking the racket behind your back. Then when the ball begins to fall, hit it.
For a smash it is adviced to use the continental grip. If a high ball is coming towards you, you should move the racket behind your back and get ready. Then hit above your head (like on a serve).