I love a good shout chorus. One thing is to compose in a range that can be comfortably sung by both men and women (unless you don't want a mixed gender gang). I like to also have some doubles stacked an octave lower too so that's something to keep in mind when finding your melody and key. Also, as a general rule it probably has to be not too wordy because a) it needs to be understood by the listener when a group sings it and b) shout choruses often inspire the audience to sing along so simpler is probably better but that's not a rule.
The best shout chorus ideas I've had have come in my car, away from my instrument or computer. I think the less you think about it the better off you'll be. It needs to feel big and visceral and fun! Hope this helps.