Have you ever seen a long-exposure photo of car headlights on a dark road? Create a similar effect. Sit in one of your locations and draw the path of every customer coming through as a line on the same map. Superimpose the lines on top of one another.
Look for patterns... the places where the carpet is worn (figuratively or literally). When you know the most traveled paths, you can think about how to use the adjacent spaces to upsell and cross-sell. Or make small adjustments to streamline the flow of customers.