Exterior Doors:

All exterior doors should be either metal or solid wood.

For added security, use strong door hinges on the inside of the door, with non-removable or hidden pins.  Every entry door should be well-lighted and have a wide angle door viewer so you can see who is outside  without opening  the door.

Sliding Glass Doors:

Sliding glass doors can offer easy entry into your home.  To improve security on existing sliding glass doors, you can install keyed locking devices that secure the door to the frame; adjust the track clearances on the doors so they can't be pushed out of their tracks; or put a piece of wood or a metal bar in the track of the closed door to prevent the door from opening even if the lock is jimmied or removed.

Tips provided by the National Crime Prevention Council and the Whatcom County Sheriff's Office  -  Crime Prevention Unit