Frozen pipes can be very damaging to your home, not to mention expensive to remedy.  There are a few things you can do to prevent frozen pipes. 

On very cold nights open the doors to any under sink cabinets that are located on outside walls (like most kitchen sinks.) This can prevent the inside of the cabinet from becoming a freezer that can lead to frozen water lines.

Insulate all water and heating lines located in unheated crawl spaces, attics, and basements. You can use foam tubes, fiberglass tubes and/or fiberglass pipe wrap.  If you notice that the same pipe freezes all the time, then you might want to consider having that pipe re-run through a warmer section of the house.

How to<br />
Prevent Frozen Pipes: Avoid DamageSeal drafts in crawlspaces and basements.  Drafts can freeze uninsulated pipes in a matter of a few hours.  Finding and identifying those drafts can prevent frozen pipes.  Consider using expanding foam sealant like Great Stuff to seal odd shaped spaces. 

Drain and vent lines can also freeze. On very cold nights, run some hot water down drains that may be located on outside walls of your home.

Keep all your heating zones above 55 degrees all winter long to prevent frozen pipes. Shutting off or lowering unused heating zones can cause water and heating lines to freeze in walls and ceilings of the unused areas, as well as frozen pipes. 

Also, even if you are winterizing your home, keeping some heat on prevents condensation and mold from forming, as well as slows the swelling of doors and other wood parts of the house.   You are better off spending a little extra on energy to prevent the pipes from freezing than paying even more for repairs.