Now is the time to check around your house for crawlspace vents open and hoses still connected to hose bibs. With the unusually cold temperatures for several days coming the likelihood your pipes will freeze increases dramatically. A few tips: Keep adequate heat in all rooms of your house. Open cabinet doors under sinks. Leave a small amount of water running.
If your water does freeze do not attempt to thaw it out with any open flames. Do not use a hair dryer or heater under your house. It is best to leave it to a professional to get thawed out as soon as possible. The longer the pipe is frozen increases the chance that the pipes will break.
Here is a link for more tips: http://www.wsbtv.com/news/news/local/19-ways-prepare-10-degree-weather/ncb96/