1. Exterior doors need deadbolts - a good deadbolt is hard to get past
2. Bolt should be at least an inch long - Some bolts are only 5/8" long which are fairly easy to force open.
3. Buy a reinforced strike plate - A lock is useless is the strike plate (the metal part you screw onto the door frame to lock the door) come right off w/a little tampering.
4. Ignore the adjectives on the package - Words like "professional" or "faultless" have nothing to do with quality. Locks are graded from 1 to 3 so look for a grade 1 or 2.
5. You get what you pay for - expect to pay at least $40 for a good deadbolt. You can always take it when you move.
Best type of bike lock
The best type of bike lock is a stubby little U-lock, usually 3.5" wide by 5.5" high. They are difficult to cut and too small to be forced open. Check out the OnGuard Bulldog Mini TC for$21 on Amazon.
Source: Woman's Day Magazine, March 2010