I would start with pole work with any horse your teaching to jump. It really depends on the horse and rider. If it is and OTTB and your comfortable with it then I would just start cantering jumps because OTTB are so use to galloping, they have a really unbalanced trot. I would canter a little cross rail . If they are balanced enough to trot jumps then start trot little jumps. I would also, work on gymnastics with you horse once thay have started jumping. It helps them figure out how to come off the ground. Do a cross rail for the first jump then put a little vertical about a stride away from the other jump. Wish you the best of luck teaching your horse to jump. I'm sure he/she will do great.
Pole work, and gradually increasing the jumps!
The key is to be calm and patient in the saddle. Repetition is key, and you have to give your horse time to get comfortable and confident. The distances and jumps will probably be weird and awkward at first, but you just have to support and encourage good effort. Get them comfortable with poles, starting with one or two, and then gradually adding more. You can also go from placing them a few strides apart to one over time.
Crossrails are a great teaching tool for both riders and horses. The horse will have an appealing option in the centre of the jump, which is where we want them. So you teach straightness, and can slowly build their confidence.
I agree with Devon! Pole work and gradually increase the height. Hope all goes well!
I definitely recommend lots of flat work over poles on the ground to teach him where his feet are. Then you can gradually increase over cavalettis and cross rails until he starts to under stand the meaning of Jumping. You could also start to free jumping him to see how much scope and jump he has. Believe it or not, one of a horses natural instinct is to jump so it isn't to hard to teach them if they are willing. Hope this helps, good luck😉