I loved listening to this talk by David Heinemeier Hansson, partner at 37signals, to Stanford University students:
Here’s what I think is the best bit (So you don’t have to watch it all!): He says all planning is guessing, especially when starting a new venture.
Sure, if you’re working with well-known commodity products and services, and you’ve been in business for a while, you can make projections about sales, revenue, costs, reach and market share. But if you’re doing something new – and it doesn’t have to be a brand-new business; it might just be a new product or service – you’ve got no clue! So don’t obsess over your business plan; it’s far better to get it out there to the market.
Steve Blank says the same thing in his recent article, No Plan Survives First Contact With Customers.
Or, as I put it: Start before you’re ready!