K.I.S.S.
You know what that means. The best ideas start out simple. Whether you're creating a drama or a documentary, focus on one main idea for your film. Get your group together and brainstorm. No idea is too silly, stupid or wacked out. Write every idea down. Don't stop to judge - just keep throwing out ideas.
Eventually, some ideas will rise to the top. Everyone - or most everyone - will have a few favorites. Are there any ideas that are among everyone's personal favorites? You don't have to get everyone to agree on which idea is best - it may be impossible for everyone to come come to the same conclusion. But everyone should agree on which idea your group will pursue. You might have to compromise a little to get everyone on board, but that's OK.
Once you have your idea...
...it's time to make it come to life. How will you tell the story? If it's about something in real life - go visit the people and place you want to film and talk to them about your idea. Tell them what you want to accomplish.
If you're doing something fictional - you'll need to recruit actors and give them words to say and actions to do. Break your story down into bit-size pieces...scenes... like this: "first this happens, then this happens, and then there's the conclusion."
Every good story has conflict. That doesn't mean a battle or a fight scene. It means that your characters - whether they're fictional or real - have to struggle to do something, or figure something out. The best films have conflict that we all relate to.
These aren't rules...
...for your film. They're just a way to help you organize your thoughts. Use your group's creativity and energy to tell your story your own way.