Warming up before starting the more difficult movements is important for the horse and rider. The muscles need to relax and become supple. Your hoses from the beginning of work must move forward, workmanlike and in a decent balance. He needs your hand for support, but not to lean against. Riding single track figures going from one direction to another is a good way to start and also helps with straightness. For example, serpentines, loops, turns and circles. It is the rider’s job to maintain a rhythm and promote a regularity in the stride. Humming or counting can help here.
Transitions must then be tested, start with a transition from trot to walk, 3-4 steps, and be disciplined to have tour horse answering the leg aid at the moment you ask. Ride some canter transitions in the same way. After 15 minutes you are set up to tackle the next level of work.
Move onto shoulder in on both sides to improve balance, bend, encouraging the hind leg to take weight which lightens the forehand. If your horse finds this more collected work difficult, move into leg yield which will open the movement and create more impulsion before trying shoulder in again.
The next step is to work on which ever movement you have chosen to train, be it changes or lateral work for example.
Finish work with something you and your horse enjoy and are good at before stretching the frame on a longer rein but still on a contact, and then you can walk your horse on a loose rein to end.