I bought a book on bits! It is based on the Myler Bitting System. They suggest using a snaffle. There are lots of snaffles. A bit has two main parts, the mouthpiece, and the cheeks. The mouthpiece obviously goes into the horses mouth. There are many kinds. The simpliest is called the regular snaffle, which has a single joint. I use a snaffle with a single joint on my green horse.
Someone mentioned a french link. This is also a good bit, it is softer than a regular snaffle and more comfortable for the horse. It has two joints with a flat curved piece in the center.
Since I don't have very soft hands, the book recommends a HBT shank. If you do not have soft hands, stay away from long straight shanks ;)
And the thing to remember about 'D' rings and eggbutts is the amount of pressure you apply to the rein, is exactly the amount of pressure applied to the horse's mouth.
*They also said that one small wrinkle should be visible at the end of the lips where the bit meets, not two or three.
Lettin' the cat outta the bag is a whole lot easier than puttin' it back. -- Unkown