Make sure you get one that's rated 3x to 4x the weight of your vehicle, and with web loops, NOT HOOKS, on the ends. You'll also need two D-Shackles to connect the strap.

Here's a video on how to use the strap:

http://www.youtube.com/watch?v=2JBnxSqpuCM

If you don't have a tow hook you can wrap the strap around the frame of hitch receiver or chassis frame and then close it with the shackle. Don't hook up to an axle, cross-member or part of the suspension, as you'll definitely bend or even remove these parts from the vehicle (I saw a guy pull his driveshaft right out of the transmission when the axle he was hooked to got pulled almost off). But most vehicles have tow hooks, or a socket into which a tow hook stowed in your OEM took kit screws-in. If you don't see them under the bumper check your owner's manual.