When I was still in grade school my mother was abducted from a suburban mall parking lot, so personal safety in a parking lot is something for me that hits home. And something that I have been thinking about for the 25+ years since. Combine that with plenty of practice from living in high crime areas (Philadelphia/Baltimore/Washington DC, Atlanta, Los Angeles, Miami/Ft Lauderdale), and I think my tactics have evolved to be pretty solid.
Actual location in the parking lot is most often of little consequence (unless you stick to parking in darkened, concealed areas, where dangers seem to abound) but here are a few tactics that can be of help:
1) Park rear in nose out: This puts you in the best position to get out of dodge quickly in an emergency. Plus, when approached from the normal lanes of travel, you can open the door towards the most likely threat axis-that allows you to keep the door between you and the bad guys, giving you time to start the engine and throw it into gear and begin escaping. Who cares if the door isn't shut, or you bash the door on other cars as you pull out...break contact and clear the area. (Many people on this forum talk about shooting an intruder into their home-something that never is a factor in that plan or decision is bullet holes in walls and blood stains on the floor. Like those things, possible auto body repairs shouldn't be a factor where your safety is concerned.) Thinking defensively as you go into a parking lot can be a big help (I drove emergency response vehicles for a long time, so this was drilled into me: park so that you can leave as quickly as possible).
2) Take an indirect route to your vehicle: this means that anyone who might be following you now has to cut across parked cars, etc, just like you have done, moving in an unnatural pattern and giving away their intentions early. If need be, make your way back into the store you have just come out of, you are safe there.
3) Keys out and in your hand, eyes up and scanning as you are walking: be aware of your surroundings. Being alert and aware makes you look less vulnerable and less of a target. Having your keys out and the car key in your hand means you can keep your head up when your reach your vehicle and be aware of anyone approaching at this vulnerable time. Plus it gets you into the vehicle quicker, reducing your time where you are stopped and vulnerable.
If the situation deteriorates:
a) Run: but not to the car, drop the bags you are carrying, head whereever you think safety is...escape fast. Nothing you have in the bags is worth what might happen to you.
b) Open area confrontation: turn and very loudly and publicly scream: "Why are you following me !?!" Now you are making the situation very public and attracting attention, at worst you look like an a$$ or some kind of nut....but you may startle someone who is stalking you enough to force their hand-and hopefully get them to split-since they have now been made.
c) Flip the Situation: as a last resort, look for a big van, truck, suv you can turn the corner of and be hidden from their view. Turn that corner and be out of sight, drop you bags, turn and be ready to attack with full fury anyone who turns that corner behind you. The best defense sometimes is a good offense, let the battle be on your terms-seize the initiative.
Being aware of your surroundings and not looking like a target is one of the best ways I have found to stay safe, even in an unsafe place. But that means putting distractions out of your mind, and possibly even out of your hands...and using your best weapon, your brain above all others-100% of the time.
Danger seems to come when you least expect it.........