I found the process of writing a business plan to be a useful one. It’s really just a list of questions to ask yourself - who are the customers? What is the product? How will you sell it? etc.

The plan itself was short enough that I could share it with a fee people for advice but I never showed it to any of my investors, other than perhaps as a way to give a pre-canned snippet of information on a specific thing.

The process itself took about a day and a half, mostly spent getting specific answers. The knowledge gained helped a lot while pitching.