This is invaluable advice from Hal of Bicycle Habitat on how to properly lock your bike. Sure it helps deter thieves if your bike is crap to begin with, but he says that most times, bikes get stolen because of improper or faulty locking techniques.

As a rule, your bike seat, frame, and both wheels should be locked in some way (either to each other or individually). If you’ve got pit locks to replace a quick release on your wheel, then you’re sorta safe in that regard (unless the thief is carrying a tool box around).

Hal also touched upon something else which rings very true to my personal experience of having my bicycle stolen. He says that thieves often steal bikes in CROWDED and BUSY areas rather than quieter streets.