Some useful guidance by Jason Lemkin, a VC. Two items on the list stand out:
The initial decision is made within 20 minutes of the first face-to-face. Make it exciting, speak with data, and get to the point. The initial Yes, Maybe or No decision is made within 20 minutes. So save slides 20–200 for questions and back-up.
Making stuff up is death, or close to it. If you don’t know the answer, just say that, it’s fine. But make something up that the VC knows the answer is otherwise … that’s almost always a No right there.