When I started my first horse from a youngster, I made the mistake of shoving the bit against his teeth to get him to open his mouth. This was, of course, not the correct way, and only resulted in him having issues with bridling for many years. So, here is the correct way to go about this task!
Position yourself on the left side, next to the horse's head, facing the same way the horse is. With your right hand holding the bridle, slide the bridle over his face so that you can put your hand over the poll and sort of between his ears. DON'T PUT THE BIT IN YET. Wait until your horse is calm and not tossing his head. You can put pressure on the poll with your right hand (or arm), asking him to lower his head if he raises it too high. Use your left hand to put slight pressure over his nose, about halfway between the eyes and the nostrils (where the bone and cartilage meet). The bit should be below his jaw at this point, and out of the way. Now, just wait.
Once your horse
begins to relax and lower his head, position your left hand on the bit, to
guide it into his mouth. You do not want the bit to clank or smack against his
teeth, so go slow and take your time. You can reach into the horse's mouth and
"tickle" his tongue, bars, or the roof of his mouth, until he opens
his mouth for you. There are no teeth in this part of the horse's mouth, so you
won't be risking any fingers. I often switch my right hand to under the horse's
neck and holding the bridle by the cheek straps above his nose while I guide
the bit. If your horse is not tossing his head, this position is more
comfortable.
Once the bit is in,
check to make sure the tongue is under the bit, and that the bit is adjusted
and positioned correctly. Most horse's that toss their head have learned to
avoid the pain they associate with the bit in any way they can, so check
everything you can think of. The general rule of thumb is that an english bit
should be adjusted to have 2-3 wrinkles, and a western bit should be adjusted
to have one wrinkle in the corner's of the horse's mouth. Also, the cheek
straps should not rub too close to the horse's eyes. If so, your browband may
be too small. You might also want someone to help you check your horse's teeth
to see if there might be any other reason the bit is bothering him.
Spend some time
every time you tack up doing this ... repeatedly. Bring your horse in, put the
bridle on and off a few times, then give him a treat and put him away. You can
also try coating the bit with molasses and/or sugar, once you are able to get
him to keep his head low for you. Often, this will help a horse associate
pleasant things with the bit in his mouth, instead of pain.
Take extra care when removing the bit NOT to hit his teeth. Let the horse spit it out. He'll appreciate it, and you won't have to deal with a horse that's difficult to bridle.
Once you can get the bit in once, practice slipping it part way out of
his mouth then back in repeatedly. While
doing this, the horse should keep his head down in an accessible position.
HANDY TIP:
I started wrapping the bit with one of 3 types of soft candy... either Bit O' Honey, Airheads, or Fruit Rollup / Fruit by the Foot type wraps. It makes it much more enjoyable for the horse, and now they typical try to almost snatch the bit out of my hand! Just warm the candy in your hand then squish it around the bit.
