Glance from side to side occasionally, pay attention to sounds around you, and leave immediately as soon as you are in your car. I repeat - get out there immediately. Many women have a tendency to get into their car at a parking lot and rearrange their purse, use their cell phone, put on makeup, or check their daytimer. A predator may be watching you. Play hard to get.
Parking garages are potentially more dangerous than most outdoor lots.
Look all around you, look into the car, and check under the car. If there is a van parked next to your driver door, get in on the other side. This is an old trick used by many predators. The view is blocked and it is easier to abduct someone than you may think. Be a DITZ and set off the car alarm if you feel the least bit threatened.