How can I determine which outlets belong to which circuit?
You can get a circuit breaker finder which is a module that plugs into an outlet to send a signal that can be picked up by the other half. The plug-in component appears to only work when the power is turned on. The receiving unit is designed to work at the breaker panel, but I wouldn't be surprised if it worked on other outlets.



Of course this is overlooking the cheap and easy answer: turn off one breaker and see what's still working.