In an electrical emergency:
Locate the circuit breakers or fuses, and know how to shut off the power.
Post shutoff instructions next to the breaker box or fuse box.
Unscrew individual fuses or switch off smaller breakers first, then pull the main switch or breaker.
When turning the power back on, turn on the main switch or breaker first, then screw in the fuses or switch on the smaller breakers, one at a time.
You should not enter a flooded basement or standing water to shut off the electrical supply because water conducts electricity.