Like others have mentioned no bike is safe if a thief wants it. Locks are a deterrent. Fortunately, most thefts are crimes of opportunity.

1. Always lock your bike. I use Sheldon Brown's method myself
2. Lock your bike in a well lit, traveled, and public area
3. Try to vary your times and places where you lock your bike
4. You can try to camouflage your bike with stickers, or taking off markings, or try making it less desirable.