The most important thing to do to prevent freezing and cracking of your plumbing during the winter months is to drain all of the liquid from pipes you won't be using. By shutting off the valve for an outdoor faucet from inside your home, you can ensure that your pipes are safe from the cold.
Turn off the valve for every outdoor faucet from the inside of the house. This should ideally be a separate valve from the rest of your indoor plumbing.
Go outside, open the faucet and let it drain completely. Leave the faucet open.
Purchase or construct a dome of Styrofoam and place it over the open faucet. Seal it to the side of the house. This will help keep any cold wind from blowing inside the pipes and freezing them. It will also help keep the faucet warmer from the heat of the house. You can also paint or purchase a black dome, which will better absorb heat from the sun and trap it around the faucet.