There are some steps you can take to up-keep the safety of your parking lot and not go overboard on your pocket.
Increase lighting in specific areas that might be a possible spot for criminal activities.
Keep all areas clear and visible by eliminating overgrown bushes, trimming vegetation around the lot and making sure the whole lot can be viewed with the naked eye from any viewing point.
Display signs of caution, and warnings that can create an impact amongst drivers, customers or any other person that might have ill intentions.
Share your concerns with neighboring businesses and their parking lot management so they can report incidents in their areas to keep you cautioned and discuss future prevention strategies.