Buyers must prioritize Cold Cranking Amps (CCA), which indicates the battery's ability to start an engine in cold temperatures, and Reserve Capacity (RC), which measures how long the battery can run essential accessories if the alternator fails. Additionally, ensure the Group Size (physical dimensions and terminal placement) perfectly matches the vehicle's battery tray to avoid installation issues. For modern vehicles with start-stop systems, Absorbent Glass Mat (AGM) technology is preferred over standard flooded batteries due to its superior cycle life and vibration resistance.