How did the tradition of the audience taking props with them to watch the show happen? I know about the rice, what else went on in the stalls???

other than the rice, there's the waterguns, the plain dealer, and the toast among others. i can't say exactly how it originated. same way it became a cult movie i suppose.

It was a dark and stormy night....
It all started with people throwing popcorn during the wedding. It was fun, non-lethal and fit into the scene Then, upon the approach to the Frankenstein place, up popped a couple umbrellas and newspapers and history was made.
The following night, people brought rice, newspapers, squirtguns and whatever else they could attach to the film. Some things stuck and others fell to the wayside...
History happens when you least expect it.

Mr(madness taking it's toll)

Don't forget the weinies for Frankenfurter!