Don't be defensive. Make it a team they will want to join. Sell the dream. The script Try to avoid painting yourself into a corner with a script that is too specific. Also, you may get a great sound bite or beauty shot that you didn't expect, and it's a sin to not use such things when available.
Flexibility is key.
When I plan a show, I determine all the elements that should be in it, then I try my best to shoot those elements on the production days. I script the show after it has been shot, using narrators to fill in where necessary. Give your video editor some wiggle room. The best shows are usually created in the edit suite, not on a word processor. It's much better to use interview bites whenever possible.