One of the best things you can do for your baby is teach him to drive.  
If you have followed any of the way-of-going, collection & round 'n down 
discussions, you will note how important it is to teach your horse to 
carry himself properly.  Driving (including ground driving) teaches so 
many of these concepts without imposing on that delicate back.
Long lining is another great way to teach your horse all he needs to know 
before you climb on his back.  If you are unfamilar with this technique, 
any qualified dressage trainer who specializes in greenies will be able 
to get you started.
Diane @ Safe Haven