Selecting a horse bit is not a task that should be taken lightly. The bit in your horse's mouth can communicate effectively or can cause extreme pain; so selecting a horse bit is not something that should be done by a novice. There are many different kinds of horse bits each with a different purpose and many working in different ways.
To select a horse bit you should understand what the difference in them are, what kind of bit your horse prefers, and have a general understanding of your horses mouth and the kind of action you want to have upon it. If you are not sure how to select a horse bit, you should speak to a horse trainer or at the very least an experienced tack store owner who can help you select an appropriate horse bit.