I know this runs the "beat a dead horse" risk, as a lot has been written about bringing folders into stores. I think this is worth reiterating and sharing:
So much of my success in bringing my folder into stores in my city neighborhood is about attitute. I mean two things by this:
1. Confident and non-chalant---as others have posted, I act like my folder and I belong in the store. IMHO, this is the biggest factor in my success in bringing the bike into stores. Security guards look at me funny, but as soon as I act like a regular shopper (hi, can you tell me where the shampoo is?) there's no fuss and no questioning.
2. Polite and enthusiastic---when asked about the bike by employees I answer all questions and talk about how much I love the bike. Today, I went to an Ace Hardware in my neighborhood. Not only did an employee working the register/till ask me about my bike, but after a cheerful discussion, she offered to let me store it behind the register while I shopped!
I guess I am saying that for me, in my part of D.C., confidence, politeness and enthusiasm work very well. Instead of going in ready to do battle I go in ready to shop.