When riding a young horse, if you can keep control of their head, then the risk of a conniption fit are minimized. I refuse to ever get on a horse without having them flexible to both sides with the bit. Lots of people will work on that on the ground by flexing the horse to the side until they give and releasing pressure. I prefer the hands-off approach. I like methods that allow a horse to teach themselves and that is what I use to teach them to give to each side. After getting them saddled and warmed up enough, I will use the bridle reins on just a regular snaffle to 'tie their head around.' I will run on rein up through the back D-ring on the saddle and then take a wrap around the saddle horn with it (as seen below).
I will shorten the rein just enough so that the horse's head is bent to the side. Short enough that they learn to give but not so short that they learn to brace. It is important for them to have enough rein so that they can find the release. Then I just leave them alone in the roundpen for a half an hour or so. I stay close by just in case they get in a jam but it is better if you are out of sight of the horse. I use this time to do other little things around the barn like water and feed the other critters. I keep a close eye on how the horse responds to the pressure from the bit. As long as they are resisting or fighting, I leave them alone. When they finally get to the point that every time they try to straighten their neck out, they find pressure from the bit, and immediately bend their head back to the side to alleviate the pressure, I know it's time to go either do the other side or work them on something else. The reason that I like this method so much is it takes away all chance of human error. Their learning doesn't depend on a person's perfect timing because they learn from their own movements, not mine, and the release is instantaneous. I don't have to worry about my timing being off and them not being able to grasp the lesson I want them to learn. This is the first session for this mare and for the sake of congruity, I will use her as an example throughout the entire post. She had just begun to find the release to the right in this picture.
Sometimes, even for me, putting my foot into the stirrup and swinging a leg over for the first time on a young horse is the most nerve racking (and exhilarating) moment of the whole training process. But I always try to follow what my Dad taught me; if you can make that first ride an uneventful one, then you have gotten started with the upper hand. The more rides you can get without the horse throwing a fit, the less likely to throw a fit they become. After you have started riding them, then the next big thing you have to worry about is usually about 2 weeks into training. Their feet are sore, their back is sore, their mouth is sore, their muscles are sore, and sometimes they just don't want to behave. Anyway, back on point. To help prevent the bucks and general squirreliness, I will always tire a young horse out from the ground before I step up into the saddle that first time. The most common method that I use is very closely related to lunging but with my own little twist. I will use an old soft rope and put the loop of it around the saddle horn, then down the off side of the horse and around their butt. While I am letting them trot or lope circles in the roundpen, I will sometimes bump or flick that rope against their butt. Some horses handle it well like this mare did and others throw a big old fit. Some will go to kicking to try to get the rope off their butt. I just keep steady enough pressure to keep them from getting it between their legs. If it gets stuck up under their tail, all the better. I have seen a bunch of people over the years get bucked off of an old broke horse simply because the horse had never had anything around their butt like that or, heaven forbid, get stuck up under their tail. When the horse starts to get tired and slow down, I will use the rope as more of an incentive to keep going. In my opinion, while this step can be skipped on younger or smaller horses, horses that are bigger or in better shape or older benefit greatly from this. The rider does too because it can prevent a lot of foolishness on the horse's part when they are too busy trying to catch their breath to try to act silly. Those older horses can get ahead of you pretty darn quick if they are fresh.
After all this is completed and the horse is nice and relaxed doing everything I have asked of them, then it's time to start preparing to put your foot in the stirrup and get on. One thing that I have found that always helps them to be a little more accepting of that first mount is to flap the stirrup leathers around some. I grab the stirrup and flop the leather around and against their side, making it pop against the skirt of the saddle. I will keep the inside rein short so that if they decide to spook, they will just go in circles instead of running completely away. When they will stand for this without flinching, I go to the other side and start all over again. When they will quietly stand for that, then it's time to start getting on. I always keep my inside rein shorter on green horses so that I don't have to spend time re-arranging my reins in case they decide to buck or spook or take off. I will also take just a moment to grab the saddle horn and kind of jump up and down next to the horse for the first time. If they are okay with that, then I stick my foot in the stirrup and begin to mount. I start with putting just a bit of weight in the stirrup at first with my rein hand on the mane and my right hand on the horn. I keep a close watch on their face to see if they plan to shoot sideways or forward to get away from me. I will then half-mount. I refuse to lay across the saddle on my belly like you see so many other people do simply because all it would take is one big jump or a spook toward your legs and you are face-planting in the dirt. Unless I have my butt in the saddle, I like to be able to just step away in the event of an explosion. If they are okay with the half mount, then I will go ahead and swing aboard. I let them sit there for just a minute before asking for them to move just so that they can accustom themselves with the additional weight. I make it a point to be busy in the saddle when I first get on. I will change my seat, wiggle and re-adjust my legs, move my feet, adjust my reins or my coat, wiggle the saddle back and forth, etc. That helps teach the horse to stand until they are given the clear cue to move forward. Not everyone is able to get into the saddle quietly and get their seat and stirrups just right the first try and I don't want my horses mistaking a leg adjustment for a forward cue and walking off before the rider is ready. When I first ask them to move out, I will keep them in a smaller circle until I know they aren't immediately going to freak out and try to dump me. The rope around the butt prep that I do also helps to prevent an "oh, sh*t" moment if they require a bump on the butt with a bridle rein to get them going. This is the first day I rode this mare. I had been on her before for a few minutes and I stopped just long enough to get my camera out of my car so I guess technically this would be the second time for everything on her. However, this is video from the first day she's ever had a saddle on or anything. So I took this mare from a spooky, snorty mess to this in just a couple of hours.