I remember back in the 90's, I brokered a deal for a friend to buy a Cannondale new from a shop owner I frequented. She got her purple H300 and was all excited.
Next time I saw her, that same frame was completely covered in duct tape. That beautiful purple had taken on a Mad Max quality. Asked her about this, response: "Best way to not get stolen."
Fast forward to now. When I'm asked for recommendations on how to prevent theft, my answer is always the same. Lock the frame and rear wheel and take the front wheel with you. Awfully hard to ride away on a bike with one wheel unless you happen to be carrying a spare, which most thieves don't.
I realize that this doesn't work as well if you have really tempting parts or other bits. But for most thieves, it's enough to make them want to pass on your bike and go for one complete with both wheels.