To unlock a car with push-button door locks, press the "unlock" button on the car's remote. If you've locked your keys in the car, use a wooden wedge to create an opening in the door, then insert a long metal rod to press the unlock button.
Insert the wedge or a door stop towards the top end of the driver's side door. Create a small opening to make space for the metal rod. Adjust the rod until you trigger the unlock button. Although this works most effectively with electronic locks, it works on regular locks as well.
Many cars feature a keyless unlocking system. The unlocking method varies depending on the system. One of the first versions was a keypad on the driver's side door, where drivers entered a code to unlock the vehicle. Other vehicles unlock automatically when the vehicle detects the key fob, so as the driver approaches the vehicle, the doors unlock for him. Other vehicles detect the key fob, then unlock when the driver presses a button on the door.
Some cars also offer keyless ignition systems. These cars start with the press of a button when they detect the key fob. Cars with keyless entry and ignition systems benefit drivers, since they don't have to carry as many keys.