If you sold your last startup for $800 million, you probably already know how to build a business, and even conservative investors won’t worry about the quality of your next business plan. But, for the rest of us, don’t believe the Silicon Valley myth that all you have to do is sketch your million-dollar idea on the back of a napkin, and investors will line up to give you money. Based on my experience as an investor and mentor to aspiring entrepreneurs in Silicon Valley and elsewhere, one of the quickest ways to kill your credibility and your startup is to offer a poorly written business plan, or none at all. There really is no excuse these days, with samples on the Internet, business-plan books in every bookstore, and dozens of apps to automate the process