Remember this - crime can happen anywhere. Night time or day time.
Always be aware of where you are. Don't get too tired or lazy to keep your wits about you. Notice if anyone seems to be following you in a parking lot or store.
Don't carry all of your gifts to the car at once - make several trips so that you are free to fight if you need to.
Look in your car before you get into it. Also look UNDER your car before approaching.
Make use of your trunk to hide your purchases. Do not fill your back seat so that people can see what you have.
When going to your car, have someone walk you out, or at least have your keys ready to unlock the car door if you need to. You do not want to be fumbling for keys at the last minute.
Keep your cell phone powered up and ON. If you need to use the phone, you don't need to be waiting precious minutes for connection.