Probably the "highest risk" situation is to be parking a bike in a rough neighborhood for hours at a time. I do most of my riding near downtown Houston, which probably the crime capitol of Texas.
If I'm going to leave a bike out of my sight for hours in downtown Houston, I combine a bunch of different security techniques:
- I ride a twenty year old bike that is scratched, dented, and beat-up looking. The bike rides as nice as a brand new $2,000 bike, but it looks like it is worth $5.
- I use the "Sheldon Brown" method and lock the rear wheel to a steel post set in concrete using a Kryptonite New York u-lock, or an OnGuard Brute u-lock. I use a second Kryptonite or OnGuard u-lock to secure the front wheel to the downtube.
- I select places where there is a lot of foot traffic. Next to the ticket booth at the movie theatre, not in the alley behind the theatre.
- Avoid most bike racks. The typical bike rack is flimsy and is weaker than your lock. I lock to thick steel poles set in concrete, looking for the thickest pole my lock will fit around.
- Park next to a brand new Trek or brand new Cannondale. Crooks are lazy and dumb, but even a dumb, lazy crack freak knows a pawn shop pays $50 for a sharp new Trek and pays nothing for a 1985 beater bike.