When I am starting horses I actually try to do as much as I can in a halter first but then I like to move them onto a hackamore as the next step. One can usually figure out if a horse is a hackamore horse or a bit horse. Some horses just don't respond very good to a hackamore and a bit is a better choice. Eventually I usually end up moving to a bit, but I want to stick to the least severe possible. If my horse is responding the way they should with the least severe then there's not any reason to put something more in his mouth.
I understand that in some training, for example barrels, one may need to switch to multiple bits to practice different things with their horse. Bending, rating, more wow and less go, can all require different types of bits and headstalls and shank lengths, so don't be afraid to put a bit in horses mouth. I only recommend starting off with the least severe so your horse doesn't become afraid of a bit in his mouth in fear of pain, or become lazy and only respond to severe bits, and wont respond as well when a simple snaffle is put in his mouth.
One will want to take off any reins that are on the bridle before first putting it on a horse. This way if for any reason the horse would spook they wont get tangled in the reins or break them, and then you'd have to buy new ones. Usually when I first bridle a horse I put the bridle on (no reins) and just turn the horse loose in a run or round pen and let them get used to it on their own for a little while. They usually chew or move their mouth around feeling the bit in their mouth and trying to spit it out, which is all normal. Once they stop playing with it I usually give them a little grain or a small bit of hay so they have to learn to eat a little with it and get used to it even more. Before you know it your horse wont think as much of it.
After the horse shows signs of acceptance of the bit that's all I like to do the first day. I'll take the bridle off, give them some good rubs and praises, maybe even a few treats, then call it a day. On the second day I will attach the reins (only if the horse shows no signs of spooking at them or the bridle) and start working from the ground on turning their head and giving to the pressure of the bit. Make sure they bend their head both directions and laterally a little too. It's better to start them early on not raising their head from bit pressure so you don't have to work on it later on.
Make sure you work this exercise on BOTH sides of the horse, as well. Once he's moving his hip keep working on just having him bend his head around and holding it there for a second or two to make them more soft and supple. This way when you get in the saddle you know you will have control of their head and their hips so they can't run off with you. It also is good because when we start doing the UP, DOWNS I will actually have them have their head pulled around so all they can do is spin a circle around me instead of bolting forward. It's safer this way for the rider and keeps the horses attention focused on the rider.
Hopefully your horse is accepting the bit, or in cases that I like, the hackamore, and responding to pressure well. Next time we will be ready to start working on "up downs" by putting weight in the stirrups and getting our horses used to us getting on them! How exciting!
Until next time,
Good licks and chews to you!