It’s been over a decade since I’ve had a bike stolen. I’ve developed a few habits that have helped prevent this; I don’t leave my bike in high-risk areas and I don’t lock my bike up in the same spot all the time, for example. But by far the best one is that I avoid locking my bike up if at all possible! This is counter-intuitive, but here’s why I believe this is important:
First, locks train you to leave your bike where it’s easily locked, not where it’s inherently secure. For example, if you go to the drug store and think, “where should I lock my bike?”, you’ll look for a pole or bike rack on the street, where it’s a ripe target for any passing thief. But if instead you ask, “where should I leave my bike?”, you’ll probably wheel it inside the store where you often don’t even need to lock it. You’d be surprised how many businesses have convenient places to lean a bike, where it’s in sight of staff and customers.
Second, thieves are good at breaking locks, we all know this. If you’re relying on a lock, you’re playing their game. Sure, you can spend $50-$100 on a super-secure(???) lock, but how good will you be about using it? It’s heavy, it’s cumbersome, you have to keep track of the key, it takes time to lock and unlock, it has a clunky chain that bangs up your paint job. Locks are just generally a pain in the ass, and the more secure (read, “inconvenient”) they are, the less likely you’ll be to bother with them. It’s a no-win situation.
Finally, a lock only secures your bike frame and wheels. It doesn’t secure your seat, lights, water bottle, repair kit, pedals… or the dozen other easily removed items that comprise most of the value of your bike. Just think of all the bike frames you’ve seen picked clean with the locks still on them! So even with the best lock in the world, you’re only securing a couple of the slightly more important bits.
Mind you, I’m not saying you shouldn’t carry a lock. They’re good to have as a last-choice option. But pick one that’s easy to carry and use (e.g. a decent combination-cable lock) so you have a better chance of having it and using it when you need it. But for heaven’s sake, don’t trust it!