Since no one is posting here I'll start.

Having trouble finding an unlocked door or window? Take a look at the hinges. If the hinge pins are on the outside you may be able to remove them and take the door right off. Some sites will have the hinges attached to the outside with the screws exposed. Unscrew them!

A great method for this is to put a screwdriver to the end of the pin (not the head, but the other end) and pound it in with a hammer. A couple of light blows should do the trick with well-used doors. Older doors take more time.

Watch out for door alarms.