When people think about starting a business, writing a business plan is usually the last thing they consider. It's exciting to dive into details, start choosing paint colors, pricing equipment. Yet starting a business without a plan is like taking a trip to a new place without a map or building a house without blueprints. You may finish, you may even get a good result, but the odds are it will cost you more time and money than if you'd figured it out ahead of time.

There's a school of thought about entrepreneurship that believes that you should just get going. Focus on the product...