How do you prepare a horse for mating?

This is for live cover; let me know if you're wanting anything else! For a mare, you wrap the tail. Get some gauze pads and warm soapy water, and wash the vulva. Make sure it's as clean as possible. For a stallion, you need him to let down his penis, and then wash it with warm soapy water. You may also want to put breeding hobbles on the mare, or a muzzle on the stallion. There is more specialized breeding equipment also available; talk to someone experienced in breeding for more information (usually, anyone who owns a stallion knows something about it).