The Moto 360 isn't a perfect device, but it's still probably the king of Android Wear smart watches for the time being. One of the cool things about the 360 is the smarter way it makes use of ambient mode (not the ambient light sensor, that's different). The screen will stay on so you can see it without the full wrist-flip gesture, but you can make use of ambient mode to save power when you're not wearing the watch—just lay it face down.
The Moto 360 knows to put the ambient screen completely to sleep when your arm is at your side or otherwise in a position where you cannot see the watch. It will also go to sleep after a few minutes of laying face up on a table. However, it wakes up and resets the sleep timer each time there's a new notification. You can keep it off by flipping it face down. It's just like having your arm at your side—the watch knows you can't see the face, so it stays off even in ambient mode.
You can use this little trick to save battery life if you're not going to have the watch on for a bit, and there's not a charger nearby. The Moto 360's battery life has gotten a bit better after the last update, so you might actually want to use ambient mode now. This little trick simply makes it more feasible. Just be careful where you're setting it down. It'd be a shame if you scratched that pretty round screen.