One tool I like to use, to help my horses connect their ground work to their under saddle work, is my voice.

When doing groundwork, I really like to teach all my horses voice commands. For example, on the ground as well as from the saddle, the voice command is a connective link for your body language. If on the ground lunging, the horse learns that when you ask 'whoa' and move your body slightly in front of the horse as well as slight pressure on the lunge, then the pressure is release and your body relaxes when they stop, they will learn 'whoa' means you want the horse to stop. So then later when you are under saddle, and you apply slight rein pressure and push down in your stirrups, you will say 'whoa' and the horse can connect stopping with the new pressures, and as a reward you relax all pressures when the horse has obeyed. The same goes for your gaits. If on the lunge you say 'walk' and move toward the horses hip and it moves forward and is praised, later when you're on the horse, and you gently squeeze both legs and say 'walk' the horse will be able to connect the two commands. Horses are smart animals, and any little bit of help we give them, they will pick up on quickly, and make the training experience more enjoyable, and can really increase the bond you have with your horse.