(when in doubt about their tonality, ask them a couple of questions they have no reason to lie about; where they grew up, if they have any pets, etc. Listen carefully to the pace and tone of the answer, then see if it changes when they start talking about a project or name-dropping)
If you are still unsure, and don't have the experience to ask questions that will surely "out" their bull, then ask someone with experience. Call a mentor, explain the project, and ask what questions you should ask and what you should have written into a contract.
(Yes, you should have a contract even if you're working for free. If you're working for free it's for footage, right? Have that in writing)
SOMETHING TO CONSIDER:
Most people are not coming from a place of "bulls*#t." They have a dream, like you, and truly believe in their project. The problem is most people who try to get their project going, don't realize what goes into making a project from start to finish. That's why so many projects fall apart in post... or sooner. It's not bulls*#t, it's lack of knowledge, money, resources, and relationships.
For more tips and articles by top entertainment industry coach, The Greenlight Coach, visit www.theGreenlightCoachBlog.com