Commit.
Improvisation requires players to engage fully with each other. Presence and projection are the premises of trust and collaboration.
Don't judge your work
Test different approaches
Learn from trials
Be in the here and now
Be part of the ensemble
Take risks
Listen.
Improvisers are sponges feeding on their surroundings. Listening gives them a common space in which to play. Without commitment, there is no one to listen to.
Acknowledge others
Pay attention to details
Play by the rules
Process information kinaesthetically, in the form of movement and energy
Adjust.
The best plots tend to emerge between - rather than within - people. The process can become effortless with practice but without listening there is nothing to adjust to.