My number 1 bike theft prevention is my bike itself. It's a raleight capri wrapped in tubes and duct tape. with a rack zip tied to the back. and a blinkie held on with a coat hanger. I work in a very secure area, and lock it up through front wheel and main triangle with one of those curly little cable combination locks. The guy who rides the DeBernardi track bike locks up with a on-Guard mini-U Sheldon style.

Different people need different locking styles depending on what type of bike they ride and where they ride it. Mine comes in at night though.

I like the convenience of leaving the lock curled around my top tube and just stretching it down to lock through the front wheel. It's all I need because there are nicer bikes right next to mine which are locked with similar locks, and it's parked beside the federal courthouse.