The function of the bridle after all is to keep the bit in place in the horse or pony's mouth. A good bit held on by a comfortable bridle made from braided string, would be perfectly adequate for everything except the show ring.
When it comes to style, be practical and keep it simple. If you've got a big budget, then no problem. Get all the bells, whistles, and coloured beads. But it's more expensive and not really necessary.
The more important thing to remember is making sure the bridle is snug and the browband, noseband and throatlash fit well and neither sag loosely nor rub his ears.
a. While tacking up or grooming secure your horse by his head collar Before removing the head collar. It's a good idea to put the bridle over the horse's head.
Take the head collar off by lifting the headpiece forward and gently over the horse's ears.
c. Bring the bridle up in front of the horse's nose while one hand holds the horse's to keep his head steady.
d. Use your right hand to hold the bridle...lay the bit over the palm of your left hand and gently lift it up into the horse's mouth. Use your thumb to press his gum in the gap where his teeth finish. That will encourage him to open his mouth.
e. Once the bit is in place, keep some tension on each side of the bridle to hold it there while you bring the headpiece of the bridle up and over the horse's ears. Don't allow the bit to bang on his teeth as this will make him wary next time.
d. With the headpiece in place, separate the hair of the forelock from the rest of the mane.
Fasten the throatlash, but not too tightly, making sure you can still get four fingers between the horse's cheek and throatlash.
Fasten noseband, but make sure you can place one finger between the horse's chin and the noseband.
Watch the following video on fitting a bridle.