Premeditated answer to "Is there anything I can help you find?"

Keep a small list of one to three records, book titles, specific gadgets, etc., close to hand and easily reviewed before visiting an interesting shop. I like an index card but a phone-list works too. These should be specific, genuine, and harder to find but not obscure to the point of obnoxiousness. Rather than just browsing your way into another unfulfilling interaction for both parties, ask for help in finding said item. This is your carte blanche to explore! I have found no downside to this approach:

Either they do have, say, "a vintage copy of A Tree Grows in Brooklyn, clothbound" and you find exactly what you wanted and get to support the small business. Or, as is often the case, they don't have said item, but you are henceforth indemnified against future browsing because they didn't have what you came into the store to find. You are now free to explore serendipitously and also to leave, when you wish, without the internal quandary of not purchasing. It works both with both very nice shopkeepers (they have done their part to help) and with snooty ones (this clueless git off the street isn't so clueless after all). Keeping this shortlist has both made exploring around so much more enjoyable for me, and resulted in interesting conversations and finding the hard-to-find treasures much more readily. It also keeps me focused and prevents guilt-purchasing to get out the door.

Caveats:

- This only works (internally and externally) if you are sincere about this list. If you don't actually want to find the item you say you are searching for, or can't be specific, then it's just a waste of their time and yours.

- There is a sweetspot on the obscurity continuum that can be a little hard to get right.