1.) My first exercise involves one crossrail or vertical, either one. I set up my jump and have a pole where the horse should take off. This way the horse gets a feel for when they should start jumping and when not. I gradually higher the jump (by inches) and usually stop around 18 inches to 2 feet. This is simple and I'm sure most of you know this.
2.) I also try a few Gymnastics with my horse. I set up a small crossrail and have the horse go over a few times until I feel that he is ready for more. Once he is ready I add a pole at the spacing of a bounce. After trying this for a while, I add a pole a few strides back. After we work on this I make the pole a few strides back from my bounce a crossrail and work from there. I take it slow with the bounce and do not add it until we have perfected the two jumps. This may take days or 15 minutes depending on the age and training of your horse.
3.) You should know, my horse is even worse at striding at the canter. Another exercise we do is setting up one canter pole. If my horse tries to rush it he is circled and until we get good striding up to the jump we remain at the same pole. I aim for the same canter I would want up to a normal jump. Most important is that once I raise the pole to a crossrail I add two ground poles, 12 feet from the jump on either side. When we approach past the pole, there should be one stride left. After the jump, the next pole helps us get straightened out quicker. I learned this tip from a clinic, forget where...
These are just a few things we work on...what do you do?