Never throw water on an electrical fire.

This will be obvious to many PM readers, but in the heat (ahem) of the moment, grabbing a bucket of water can seem tempting, if unreasonable. Water conducts electricity (this is why you don't want to be in a lake during a lightning storm), so throwing water on the fire could cause it to get larger. Instead, use your chemical fire extinguisher.

Use your fire extinguisher effectively.
Firefighters recommend the time-honored PASS method:

Pull the fire extinguisher's safety pin.
Aim the extinguisher nozzle at the base of the fire.
Squeeze the extinguisher's handle.
Sweep the extinguisher's nozzle in a side-to-side motion until the flames are out.

Sure, it sounds easy, but let's hope you never have to use this advice. Start by paying attention to what the circuit breaker is telling you. If it trips immediately, evaluate the situation if you are electrically competent or call an electrician. Don't call Pat, though; he's already got enough to do.

Aside from blatantly obvious electrical malfunctions that lead to flying sparks or circuit breakers that trip repeatedly, you should always keep a sharp eye cocked for more subtle telltale electrical-danger signs: