Running the engine allows the alternator to recharge the battery, counteracting self-discharge and parasitic drain.

Start the car at least once every 1-2 weeks.
Let the engine run for a minimum of 15-20 minutes. Ideally, take it for a short drive to allow the alternator to charge more effectively than just idling.
Ensure electrical accessories (lights, radio, AC) are turned off during this charging run to maximize power going to the battery.

N/A - A no-cost method if done regularly, but may not be sufficient for very long storage or weak batteries.

Start and Run the Car Periodically