My mare is built naturally downhill, but it doesn't help that she gets extremely forehandy and refuses to engage her hind end. I've gotten tired of being pulled down the entire ride and am hoping for some tips/exercises to get her more "up" and balanced. We already do lots of transitions, direction/speed changes, backing up, etc.
My horse's tendency is also to be on his forehand, but it takes a lot of time and consistency to change that. One of the biggest issues in developing self carriage, at least for me, was making certain I didn't contribute - so I work very hard at not giving my horse something to resist against. The other (and I can hear the phrase ringing in my ears - my trainer says this all the time) - self carriage begins on the ground. Even when I lead my horse, I ask for forward and lightness up front, and have him stepping well under himself from behind. And I make sure that I am walking the same way - they are incredible mimics.
It's give and release. If I give an aid and hold, then he has something to resist against. One thing we can do, if he is not moving into a rein is, ask for the other bend, praise when he offers even a try, then ask for the original bend, etc. It is so easy to fool yourself into thinking that you are all lightness, when you're not either. So it's ask, release, ask, release, maybe you have to ask with increasing degree, but it's always that quick release - give your mare the chance to answer correctly, then praise.
First, shoe the front, and only the front. I do Eponas with Vibram pads. It gives a hair less than 3/4" height boost because the Eponas float on the footing (plain shoes sink, you need something with a large surface area like Eponas).
Make sure your farrier gets the breakover correct. It can make a big difference in a bad way if it's too far forward or back.
Second, get in the habit of never looking at your horse's lovely neck. This is the hardest one. But sit back, and then sit back a bit more. When you find yourself being leaned on, lift your hands and rock your shoulders back. Don't yank the head up to the horse hollows, just lift the hands a bit so that there is nothing really to lean on, and rocking your body back helps sit the horse down on his haunches. I'm not talking sitting on your pockets. Think more about doing it from the shoulders.
Then don't be afraid to use some more leg if you need more activity.
But the shoes were the biggest help. Maresy goes from moving like a dumpy QH to moving like a nice, semi-fancy horse. She can go from tripping over herself while muttering through a training level test barefoot to doing half steps a couple days later in her sneakers (as my friend calls them).
It's not the transitions, lateral work, etc itself-it's the quality that matters. First you have to make sure you, as a rider, are balanced in the saddle. If you're not, the horse can't be expected to balance himself. Then, you have to ride always thinking "up" and "forward". By that I mean, do not let the horse pull you down and off balance. Keep the contact, and always use more leg. Even in your downward transitions, use leg. If not, the horse will fall on the forehand and the value of the transition exercise is lost.
Keep in mind that the "contact" is like a cycle of energy from the hindquarters/your leg over the horse's back, through the neck/mouth and back to your hands through the reins. I hate buzz phrases like "on the bit" and "frame", etc because they don't even begin to convey the meaning of contact. Once you understand it, you'll know how to fix the problem of horses being on the forehand because it just makes sense. It's synergistic.
Do you have a trainer? A good one? If not, get one, because eyes on the ground are invaluable to confirm what you're feeling. A good trainer will ask you questions like, "how did that feel that time?" and over time you'll start to form a mental/physical "picture" of what it's like when your horse is working properly (I'm purposely avoiding all buzz words. )
I hope that helped somewhat. It's not always easy to be clear when describing these things, but I tried.
I saw the angel in the marble and I set him free. - Michaelangelo