I was thinking about the opposite as an idea. When you go somewhere that is likely shopped, but you are not shopping the place at the moment, maybe consider doing obvious things like taking pictures of receipts, food, asking a question just because, etc.
If they think you are shopping, you should get better service. Now, this assumes you go to places when you are not shopping them. I am sure we all have heartache when we are going somewhere that we know likely is shopped, but is not available (rotation/too late in the month/missed the sign-up/etc.). I think this is particularly useful in retail and restaurant of all kinds.