U lock it (well), or you lose it.

Image: phule

Bike thieves are working the Dallas CBD (and probably Deep Ellum and Uptown), so be sure and take all the precautions you can. They seem to be targeting parts (hmmm... swap meet?), in part because too many people don't lock their bike up properly. I see nice bikes (and beater bikes with nice parts) poorly secured downtown, and have left a few notes on bikes about being more careful. I see bikes with Brooks saddles (newish) with an unsecured seat-post quick-release (bye-bye Brooks), great wheelsets with the bike frame secured to a rack or pole, but the wheels unguarded. New panniers, lights, computers, and even fenders are all easy pickings for thieves.

Nothing can stop a determined thief, and a bold thief will strip a bike with people standing right beside it. Your job is to slow them down (tough for couriers, but easy for commuters). A good U-lock, and a cable you can thread through seat rails provides good (but not perfect) protection. Remove your front wheel and run the lock through the frame and BOTH wheels, or just through the frame and rear wheel, and carry your front wheel with you.

From Kryptonite:

Bicycles

1. Always lock your bike, especially at home. This means in your garage, in your apartment building and your college residence hall. If you have a sense of security and become a little lax, that's when a thief will take advantage.
2. Lock to a fixed, immovable object like a parking meter or permanent bike rack. Be careful not to lock to items that can be easily cut, broken or removed like a chain link fence (yes, thieves are that creative). Be careful that your bike can't be lifted over the top of the object you've locked it to, like a sign.
3. Lock in a well-lit area with a lot of foot traffic.
4. Lock in a location where there are other bikes. The chances are pretty good that there will be a bike with less security, or no security, right near yours. Thieves will go for the easiest target every time.
5. When using a U-lock, position your bike frame and wheels so that you fill or take up as much of the open space within the U-portion of the lock as possible. The tighter the lock up the harder it is for a thief to use tools to attack and twist your lock.
6. Always position your U-lock with the keyway facing down towards the ground, but not close to the ground. Locks on the ground are more easily leveraged for attack.
7. Always secure your components and accessories with a secondary cable lock. This includes quick-release components.
8. For the greatest theft protection use two locks such as a U-lock and a locking cable. The longer a thief will have to work, the less likely your bike will be stolen.
9. Don't lock your bike to itself by simply locking the front wheel to the frame. A bike 'locked' like this can easily be lifted and carried away.
10. A thief may notice a pattern and target your bike if you lock in the same location all the time. Mix up the locations a little bit, especially if you are a commuter.
11. Check with area law enforcement agencies and read all signs in the area before locking your bike. Don't lock to anything illegal.
12. Always check your lock before leaving your bike to be sure you have secured it properly.

A tip o'the hat to CJ.