You know, it's funny how you often do things without realizing it. I've been thinking about this, now that you've mentioned it.

Whenever I'm out for dinner or in a bar, I do have a tendency to put a napkin under my glass whenever it has condensation on it (i.e. a cold beer on a hot day) if it is on a wooden surface.

With a glass surface though, I'll generally wipe the glass and put it down directly on the surface.

I wonder where we get our habits.