Read somewhere that if I want to be super safe I should not only cut the breaker, but also use a voltage detector to be 100% sure there really is no current.
Looking on ebay they are real cheap:
It says the voltage sensitivity is 90~1000V AC. Can I use this to test light switch fixtures? Is the voltage sensitivity right for this purpose? They are so cheap I want to be sure the voltage sensitivity range they are rated for is adequate.