If you can reach the main breaker without touching damaged equipment or standing in water, switching it off removes power from the affected circuit until a technician arrives. Keep family and pets clear of the area, and don't attempt to touch, move, or dry out anything that looks damaged, wet, or scorched.
For fire, smoke, or active arcing, call 911 first — get the fire department moving before anything else. For an electrical hazard that isn't actively burning, such as a hot panel, a dead circuit, or storm damage to the service, call Koryente directly so a technician can isolate the problem and make the condition safe.