It's pretty wide open, since guys bring lots of different gear. The trick is to put a sequence of combinations and sequences of changes together that will sound good, and be both informative and entertaining.

We might start out holding source, pre and speakers constant and run through a string of amps, then swap some tube on the amp we liked best, then run through a series of speakers. It's always time to change when the chatter level over-runs the music.

Flexible yet coherent - a tough combo!

You've got the personality/goals of the room "host", the gear on hand, and the personalities/goals of the "visitor" to meld together. Not simple, is it? I suspect it helps if everyone keeps firmly in mind that this should be BIG FUN!

Keep your ears and your mind open.