Whats the best way? Friend taught me a neat trick the other day.. testing a power line with a lightbulb..

Erm, i mean to make sure its working, and so on.

 

Just happen to have it laying around with bare wires. Like I tested the power wire with it before hooking up the amp, then I tested the amp after hooking it up.

Or you can use that thingy that reads the output of the amp, and tests the leads on the circuit, whatever its called.