Don't worry about trot OR canter until you as a rider and the horse as the 'ridee' can do this at the walk.. in a nice safe location like the arena.
Use 1/2 or 1/3 of the arena (if you have a full size arena) and work on bending.. circles and so forth. LOOK WHERE YOU WANT TO GO and think HOW TO GET THERE. You will need to sit up straight and relax to do that.
When you ride a circle, look at the CENTER of the circle and work to keep the same distance from the center so your circle is ROUND. Same with Serpentines.. look to the center of the half circle.. then ahead for 3 strides of straight and then to the center of your next circle.
Get him extending at the walk. Get all you want at the walk. I suggest this for two weeks (riding at least 5X a week). When you get what you want at the walk.. then along the long side of the arena on a LOOSE rein, ask for a trot and then, do all the same stuff with a little more contact (not much) at the trot using half the arena.
@Punk's Tank: Successful male riders do NOT sit flat on the saddle in a chair seat. They put their weight in their heels and get their butt off the horse's back. Yeah.. I know.. the physiology.. LOL but these same guys have no issue riding those "crotch rocket" motorcycles do they?
Riding is exercise and interactive and you cannot sit the horse like a sack of sand! If you do the horse is going to have to work a LOT harder and probably will have more trouble balancing and may never become elastic.
There is something about the outside of a horse that is good for the inside of a man. ~Winston Churchill
) Dinosaur Horse Trainer