Disconnect and drain outdoor hoses.
    Detaching the hose allows water to drain from the pipe so an overnight freeze doesn't burst the faucet or
    the pipe it's connected to.

Insulate pipes or faucets in unheated areas.
    It's best to wrap water pipes in unheated areas (such as the garage or crawl space) before temperatures
    plummet. You can find pipe wrapping materials at any hardware or building supply store.

Consider installing "heat tape" or "heat cable".
    Install "heat tape" or similar materials on all exposed water pipe (i.e. exterior pipe, or pipe located where
    the temperature might drop below freezing). It is relatively easy to install and can be found at your local
    hardware or building supply store. Be sure that you use only UL-listed products and follow the
    manufacturer's instructions carefully.

Seal off access doors, air vents, and cracks.
    Winter winds whistling through overlooked openings can quickly freeze exposed water pipes. DO NOT
    plug air vents used by your furnace or water heater.

Find the master shutoff valve.
    Usually located where the water line enters your house (or near the water heater or washing machine),
    the master shutoff valve turns off the water to the entire house. Paint it a bright color and make sure
    everyone in the household knows where it is.

Check with your water company.
    Various additional precautions (such as letting a small trickle of water run from the faucet or covering
    outdoor meters) may need to be taken depending on local circumstance. Contact your water company for
    additional measures.

What if it's too late?
    During an extended cold spell, your pipes can freeze, even if you take all the proper precautions. If you
    think you know where the freeze occurred and and want to try thawing it yourself, the easiest tool to use
    is a hair dryer with a low heat seating. DO NOT under any circumstances use an open flame. Using the
    hair dryer, wave the warm air back and forth along the pipe. DO NOT heat only one spot on the pipe, as
    this can cause it to burst. If you don't have a hair dryer, you can wrap the frozen section with rags or
    towels and pour hot water over them. It's messy, but it works. Be careful when heating the pipe. It may
    already be broken and just not leaking because the water is frozen. When you thaw it out, the water
    could come gushing out. Be ready to run for the master shutoff valve if necessary.

This video shows you how to shut off your water.

Source: American Water Works Association; www.drinktap.org