DO NOT buy one until you check the reviews.  Amazon is a great resource, but a quick internet search will be enlightening.  If you are like most folks you'll stop by Wal-Mart or Gander Mountain or Dicks's and look at cameras.  Write down (or if you're lazy like me take pictures with your cell phone) the make and model and check for reviews.

My first camera I just bought what was available to hide near the back door and see who came when we were not home.  I got lots of shots of the driveway with it.  Cars would drive past it and by the time it triggered were out of range.  I did a search and found a slow trigger time was the man complaint for this model.  A year or so later I bought another one. I did my due diligence with it and have been very pleased.