Well, you cannot 'teach' them to go on the bit or in an outline, only help or guide them. All horses are capable of this. However you must know that it is more then just your horse's head being in a pretty place, it is about the horse using his back and hind quarters properly. This means you must first learn about your seat. You have to have the right balance, You should not be sitting to deap in the saddle as this will prevent the horse from usung there back muscles properly. You should be pushing your weight into your heels, and being sure you are loose in the knee and are not gripping with the knee, as this too will prevent your horse from using its muscles properly. You must also ensure your hands are not to low, make sure they are lifted up with your thumbs on top as this will create a straight line from your elbows to the bit, and allow the horse to soften its mouth. You must ensure your riding is comfortable for the horse (EG. Dont be falling down on the horse in rising trot, and dont bounce out of the saddle and slam down in canter). After all this is accumplished, you can use gentle aids to encourage the horse into an outline. To do this, you need to use a seat into hand motion. If you squeeze (using your fingers only, not moving your wrist/elbow) almost like your squeezing a sponge alternatively in each hand, and make sure you have your leg on there sides to push there movement into this. Once the horses neck and back rounds you must relax your aids, but still keeping a contact, and just squeezing every now and then. You should not however force your horse into an outline, as this will cause the horse to be uncomfortable, and will anger the horse. This may take a while for your horse to hold it as he/she will need to develope the right neck/back muscles, but the resluts are amazing, riding a horse that is naturally in an outline and is working correctly is a truely breathtaking feeling. Hope I helped!