To save a life, first assess the situation for safety. If someone is unresponsive, call emergency services immediately. Check for breathing; if they are not breathing, begin CPR by performing chest compressions and rescue breaths if trained. If the person is choking, encourage them to cough. If they cannot breathe, perform the Heimlich maneuver by standing behind them, placing your arms around their waist, and thrusting inward and upward. Always stay calm and follow the instructions of emergency responders until help arrives.