Ensure the team is comfortable working together. A collaborative effort is necessary to work within the short time frame allowed for preparation, and to win points for teamwork. Teams should practice listening to each member's ideas and building their approach. Arguments and hardheaded behavior can slow down the team's response.
Experiment with a lot of materials so the team learns new ways to manipulate them. You may want to give students squishy objects such as salt dough, stretchy objects such as rubber bands, flimsy objects like paper and hard objects such as pieces of wood. Have the team brainstorm to come up with ideas for using the objects.
Ask team members to think about plots from familiar movies, television shows or plays and give ideas about what might have happened if something had broken or if the scene were drastically changed. Have them perform the changed scene. This is a fun way to practice thinking outside of the expected based on something they know. In an actual Destination Imagination Instant Challenge competition, the team could have to conceive the whole thing as they respond to the challenge.
Practice at least one mock Instant Challenge every time you meet. Not only do the team members love Instant Challenges, they benefit from the practice of coming up with wild ideas. Imagining is like exercising; the more you do it, the better you get at it. Destination Imagination has a number of resources with Instant Challenge ideas, including some that are free.