Now take a walk around the building. If you came back during business hours, you could do further checking on locks, and the burglar alarm, see where the money is kept, find out when there's a lot of cash on hand and where valuable merchandise is displayed. These are all things a would-be burglar looks for. He's trained to spot security gaps, point them out to you, suggest improvements. Then it's up to you to follow through.
Lighting destroys the cover of darkness burglars prefer to work in.
Inside lights are particularly important around the safe and cash register. Valuable merchandise should be illuminated too- but try to keep it out of display windows at night. Arrange your stock so that a burglar working in a far corner of the shop could be seen by someone walking by. If you have a burglar alarm, make it obvious- put a decal on the door or window to make it visible from outside. Don't provide other kinds of cover for a burglar- stacked boxes, a vehicle parked close to the building, ladders, and so on.