Or, don't write a business plan...

A business plan is a work of fiction, anyway. If you don't have much experience in business, or the market is new and unknown, a business plan might be a waste of time, or, worse, a path to self-delusion. Plan just enough to make your first sale.

• The main thing is to make at least one customer happy, and complete the entire cycle of "make product, sell product" as quickly as possible. Then you will have a business, and then you might be in a position to understand some problems of the sort that extensive planning can help solve.