Recently, a business partner came to us with a request: ​could we create a list of the top marketing planning mistakes, on a single page, with some simple advice on how to avoid them? ​

The passion of the resulting internal debate about what should be on the list—and in what order—gave rise to an idea.​

​We sent the original list to our clients with modest expectations for response. We asked: “Which mistakes would make your top three?” and “Which marketing planning mistakes would you add to the list?” ​