Entrepreneurship is 80% sales and marketing
by Dries Buytaert
Other than the standard things (an idea, passion and the willingness to act), the most important thing that aspiring entrepreneurs need is the understanding that 80% of entrepreneurship is sales and marketing. If as a founder, you're not obsessed with sales and marketing, you're a liability rather than an asset.
You don't have to be the best sales and marketing guy (I am far from that), but you better enjoy getting other people excited about your project, company or product. It will help you not only with finding customers, but also with recruiting a world-class team, raising venture capital, and more. So if there is one thing you should learn before starting a company, it is "sales and marketing" (in the broad sense) — and you better be passionate about it, because you'll invest years of your life to selling and evangelizing to make your company a success. Without customers or a team, you won't need any other skills, because you'll be out of business.
You need to be talking about your idea all the time. Too many entrepreneurs believe that if they build a killer product, customers will come. It almost never works like that. Smart entrepreneurs do it backwards; they find customers first and build their product only when they have customers ready to start paying. Not testing the market by selling from day one can lead to months, if not years, of wasted time and money. So stop being so secretive about your idea. You will never find your product-market fit by keeping your idea secret until it is perfect. If you're afraid of people telling you that your idea is stupid, chances are you may not be ready to be an entrepreneur.