According to the National Crime Prevention Institute, if an intruder can't gain entry to your home in 60 seconds, he'll likely give up and move on. And since quality hardware takes longer than that to crack, most thieves won't bother.
The standard key-in-knob locks found on most entry doors actually offer very little protection. The beveled end of their spring latch makes it easy to defeat the lock by inserting a credit card between the door and the frame.
If your entry doors have key-in-knob locksets, augment them by adding dead-bolt locks. Choose a model with a rectangular bolt that has at least a 1-inch throw into the door frame.
Single-cylinder dead bolts open and lock with a key from outside the house and a knob or lever from the inside.
Double-cylinder dead bolts require a key to open or lock the door from either side. They may be a good choice if the lock would be accessible by breaking out adjacent side lights, for example. With this type of lock, however, you should take steps to make sure that you'll never be locked inside in the event of a fire. Keep a key nearby in a safe location.