This is an open invitation to the joy rider . Never hide an extra car key under the hood. Lock valuables in the trunk. This is important for both your personal safety and the protection of your car and its contents. Carry it with you.
Engraving helps in the recovery process.
Some thieves specialize in lifting the door locking buttons with a coat hanger. Consider purchasing smooth, non flared locking buttons. When moving into a new apartment, have all locks re-keyed. This can be done by a licensed locksmith and is relatively inexpensive. Dead bolt locks should be installed on all exterior doors.