I'm in Florida, and bike thieves around here look for unlocked bikes parked outside homes, and just ride off with them. I'm not in the city, though, where most bikes are stolen. I have two bikes in a locked building attached to my home. Each of the bikes has a heavy duty cable lock through the wheels and attached to other things such as a hand cart (dolly). When I'm out on a ride, and I stop at a fast food place for coffee, I have a heavy duty 'D' lock for my fat bike. It fits perfectly around the tire and rim; that makes it unridable. A cable is attached to the 'D' lock to be wrapped around a post. Then I sit inside the fast food place where I can watch the bike in case someone takes an interest in it. I am also armed in case I should have to deal with a belligerent thief. As careful as we may be in securing our bikes, some thieves carry battery-powered grinders that can cut through a chain or 'D' lock in seconds. No self-respecting thief is going to carry bolt cutters.
I also registered my bikes with the local police who photograph the bikes, record the serial numbers and put a sticker on the seat tube. The officer who did my bikes said that if a thief takes the bike, he will likely remove the sticker. There might be a very slim chance if it's stolen and I report it, immediately, and a cop happens to see it and stop the guy, I might get it back, but most likely I'll never see it again. Bike thefts in Florida run around a million a year, and very, very few are ever recovered. Bike insurance is prohibitive. The last time I checked it was going to cost $100 [£71.50] a year. My fat bike cost me $1,700 [£1,225]. It will be five years old, this year, and I have no idea what it's current value is. It's not really worth insuring it.