While my associates may grow tired of hearing me utter the phrase, few concepts are more pertinent to marketing. "The world is a bell curve" is a marketing universal constant. It applies to EVERYTHING you do. There is a bell curve for weight, age, intelligence, and more appropriately for marketers, beverage consumption, desire for gadgets, length of time people keep a car.
Understanding this basic concept is crucial to developing an effective marketing plan. Of course you start with your product positioning and target market, but then you must apply the bell curve. Realize that whatever you produce - assuming it is a viable product, you will have one end of the curve embrace it whole heartedly, typically the early adopters. These folks are fairly easy to market to, they will buy anything as soon as it is available. Unfortunately we all wish there were more of them. The other end of the curve contains the "never going to buy anything new" group. You cannot frustrate yourself trying to reach them - just let it go. The middle of the curve - and the consumers on both sides of the middle - focus your time there. The better you can define what rings their bell - the more successful you will be.