When trying to solve a bucking problem horse, training can be a challenge.
There are two types of "bucking horses" one who is determined to get you off his back and blows up and the other who is a crow hopper as if testing what his rider will do.
If you have the blow up type horse and do not feel confident to get on him, find a trainer who will.
A bucking horse is a danger to anyone who gets on him and is not worth getting hurt over.
It is possible though, with training, to get it under control.
If your horse is more of a crow hopper and you feel confident to get on him, there are exercises you can do to help him get through this.
There is no cue to tell the horse to "stop bucking" but there are cues you can give the horse to take his mind off of bucking.
When you get on your horse keep his mind busy by teaching him to respond to cues such as giving to the bit properly, lowering his head with a cue, turn on the forehand by using the bit, etc.
Once he is consistent in all of these cues pay close attention when you are riding him.
Anticipate when he is about to buck then give him a series of rein cues.
When he responds to these cues, immediately reward him by releasing the rein then ask for another cue until his mind is off bucking.
The goal here is to get him to respond to what you are asking him to do rather than what he wants to do.
Don't punish him for bucking just give him another job.