You must plan in the real world, with facts, not fiction. In other words, don’t plan “in a vacuum”. I can’t tell you the frequency with which I’ve seen this one – an entrepreneur with a “great idea” that he or she cooked up over coffee or drinks, entirely isolated from the target market. Related to the “show me your first five customers” rule and the “don’t drink your own bath water” rule, this one is meant to strongly caution you against planning a business based on an unconfirmed reality (a fantasy). We all say we won’t plan in a vacuum, but the reality is that correctly planning for a business is hard work – it takes a lot of time and resources, and it’s frustrating. It’s so much easier just to make up your own facts and go from there. Don’t be tempted – sure you can try to define your own reality – but just make sure that your reality is at least grounded in some facts. First and foremost, make sure that your venture fills a legitimate need. Next, make sure that there are people willing to pay for your solution. Last but not least, make sure that you can make a solid return by providing your offering at a price the market is willing to pay – a sufficient return to make it worth the risk, time, effort, and other resources you will need to commit the venture.