Personally, my prerequisites before I get on is that the horse has to be able to move the hind end and forehand, be able to walk, trot, canter, halt from my voice, Back up, side pass, and be comfortable tacked up. They should be able flex their neck on each side from pressure with whatever your planning on using for your first few rides (snaffle, side pull, whatever). This is important because a one rein stop serves as my breaks for the first few rides.
Then I’ll practice sticking a foot in the stirrup and jumping until they’re comfortable with that. Then I’ll practice getting on. The first thing I do when I get on, is get off. This way the horse knows that I will eventually get off and that makes them relax. So I’ll practice getting on and getting off and they should stand still while I give them lots of rubs and maybe some treats.
Then I’ll ask for a flex from both reins but the horse should already know how to do this because of the ground work. Then I’ll add a bit of leg and ask the horse to move the hind end. Once we have that down, then I’ll work on going forward. This part is scary for babies and they mig be very resistant to moving forward not because they’re “stubborn” they just don’t know what you want. Sometimes it’s best to have a friend on the ground helping you in a round pen.
To go forward I will start by kind of lightly bumping with my calves or lightly tapping the hind end with a dressage whip and trying to just create momentum. I’d avoid squeezing because it makes them claustrophobic and they probably already feel that way. When he walks forward (direction doesn’t matter so don’t get picky) I stop. At first, be happy with a few steps. Then work on it more so that when the horse is walking forward you’re leaving him ALONE. So no leg, no clucking , no tapping, no steering, no contact as long as he’s walking forward. When he stops, bump with the calves, cluck, tap with your crop, whatever. Make walking forward relaxing, and stopping uncomfortable. When you have a calm, forward walk then you can do the same thing for a trot and a canter. For stopping, your horse should know “whoa” from your ground work but if things get bad you can use a one rein stop too.
Then I’ll work on steering. When I start to teach this, I’ll use a guiding rein and just ask for them to go in that general direction and then leave them alone. Start small with what you’re asking. Don’t steer the whole ride, steer for a few steps here and there and let him decide where he really wants to go.
The two biggest mistakes I think people make when they start babies is that 1) they get too picky. He’s not going to go collected, in the direction you want, or straight, just take what he gives you and ride what you get for now. The second biggest mistake I see is when people ride the same as if they’re riding a broke horse. You shouldn’t look like you’re going to win any equitation medals. When I’m doing a first ride my legs are off my horse with my heel almost braced down. My reins are loose, and when I eventually start steering, my hands are low but far out to steer because I’m trying to make it clear to them and not worried about looking pretty.
Good luck and most importantly, go slow. You don’t have to do all of that in a day or even in a week. If you do things right, you won’t have fireworks for your first rides. Think about only asking your horse do to things he pretty much already knows how to do if that makes sense.