- Do a Mexican wave (audience making fluent waves with their hands above their head).
- Have he pianist/keyboard man make all kinds of sounds and have the audience 
imitate them
- Ask the audience to stand up and do some physical warmup. Have them shake 
their arms and legs.
- Have the audience introduce themselves to strangers, tell a secret their 
spouse/partner doesn't know about to a stranger, have them hug a stranger
- Do an interview with the audience, where the MC is one character (say, a 
headmaster) and all of the audience another (say a naughty child). The audience 
needs to reply to the interview in one voice (all saying the same at the same 
time). Not an easy one, and if the audience does not feel like doing this it 
really sucks. When it works it's a real thrill.
- divide the audience in 3 or 4 groups, and give each group a sound. Rehearse 
the sound with each group. Then tell a silly story, and use these sounds as 
sound effects. (I saw a pretty gruesome one in which one group was a car 
(roar), another a dog (bark) and the third group got a kind of splashing sound. 
The poor dog got run over by the car... not exactly nice but the audience had 
fun with it)
- Do a cheering competition between the men and the women.
- Rehearse different kinds of applause (from the 'polite' applause when a scene 
sucks, over an 'ooh' appause for a touching scene, to a wild roar for a 
hilarious scene). Have them rehearse voting for a team by cheering the team 
name (if that's your format). Rehearse a 'Die' if you're going to be playing 
scenes in which the audience can decide to throw a player out of the game.

In general, part of the warm-up routine is to explain what is going to happen 
and what we expect from them, explain that we might need volunteers, 
suggestions, reactions. It's always nice if all that is incorporated in the 
warm-up.