Great article courtesy of Fox News
1. Get a U-lock. The overwhelming majority of stolen bikes were locked with a cable or chain, or weren’t locked at all. The cheapest U-lock is better than the best chain. Locally, Home Depot carries entry-level U-locks for around $14. Online, you can get U-locks from Bike Nashbar for $9. Higher quality locks are available at bike shops and sell for $25-80. Remember, a bike being unlocked is a bigger factor in whether it gets stolen than how expensive the bike is.
2. USE your U-lock. Of course this sounds like a no-brainer, but I can’t count how many people (myself included) who have lost bikes that they left unlocked “just for a minute”. I once had a bike stolen from my front porch that was only out there for twenty minutes after I got home. Lock your bike religiously. If you’re at a store and there’s nothing to lock your bike to, at the very least lock your bike to itself. (That is, lock the frame to a wheel.) That way, someone can’t ride off ON your bike (although they could still throw it in the back of a truck and drive off with it).
3. Put the U-lock through the frame, not just through a wheel. If you lock just a wheel, a thief will simply remove the wheel and walk away with your bike frame. For best protection, put the lock through BOTH the frame and the front wheel when locking your bike to something.
4. Be careful about the ends of bike racks. Some bike parking racks are constructed with simple nuts and bolts on the ends. If you park your bike on the end of one of these racks, a thief could disassemble the end of the bike rack with a wrench, and slide your bike off it. By the same token, also check to make sure that the part of the rack you’re locking to is solid and not broken at the top or bottom.
5. Don’t park on traffic signs overnight. A determined thief can take the sign off the top of the pole, and then slide your bike over the pole.
6. Don’t park your bike overnight in public if you can avoid it.
7. If your bike is expensive and you have to leave your bike parked in public overnight or for a long time, consider getting a second, less expensive “beater bike” for those times. That way it’ll be less likely to be stolen, and if it is, you won’t be quite so heartbroken. Note, though, that a poorly-locked cheap bike is often a bigger target than a well-locked expensive bike. (The smallest target is a well-locked cheap bike, of course.)
8. Paint over expensive brand names or scratch them off. Simply adding stickers won’t fool a thief into thinking your bike is old or low quality (although it may make it easier to identify if it IS stolen).