Earlier this week, I stopped at a deli for lunch and the clerk behind the counter asked "Do you need a bag for that?" I hesitated... then replied, "sure, I'll take a bag."
Although this might seem like a harmless overture, they way it came out, I felt slightly uncomfortable replying yes. Of course I didn't actually need one.
But in this situation, a small gesture that would make a world of difference would be, "let me get you a bag for this?" The customer can refuse the offer but won't feel like its a burden to accept it.
Such subtly might sound nitpicky; but it's also the difference between hospitality as opposed to customer service.