Working at a restaurant in the mall is awesome $$$$$ wise but getting a parking spot in the afternoon is not fun. One trick I use is to watch anybody with shopping bags going back to their car.
You also want to ask the person where they parked so they don't skip rows and you won't be out of a parking space. Another trick I've used as well is I've offered a person $5 for a parking space and told them I needed to get to work on time. If they are a shopper a lot of times they will feel bad for you and just tell you you can't have the spot I have done this dozens of times and it has always worked