Part 1 and Part 2 of this article covered the first 10 of the 13 worst marketing mistakes. Here are the remainder.

10B. "We know who you are, and we know where you live"

That's great if you're the IRS and are itching to do an audit. But if you're Marketing, choosing a target is merely what logicians call a necessary but not sufficient condition. Remember we discussed having a strategy for winning and a plan for executing? They had better be based on deep insight into...

• Which targets (if multiple) need what
• How those needs exist in the context of their own lives
• How our product fits that context better than any alternative
• Which ear they prefer to be whispered in while we endeavor to convince them that we are in the boat beside them, their most trusted partner in this particular and specific corner of their lives

It's not enough to describe their behavior. Facts won't do. We need to know them inside out. It's called developing insight, and it's hard —and necessary. Facts describe your target today. Insight opens the potential of imagining that target tomorrow.

If anything, the tendency to forget this most important Marketing 101 lesson (It's About Them, Stupid) has become worse in the past decade with the realization that consumers often express a general satisfaction with the status quo.

Many of us have had the experience of consumers hating the concept but loving the product. Doesn't that mean they don't know what they want? We know. And so, after years of learning to let consumers guide us, we have relearned to listen to our instincts.

But even at early stages on innovation, we need a hypothesis about who we are trying to serve and why they should care. In what unique way will we solve what specific problem? How might we make their unique lives better? Would you rather attack those issues with generalities or with deep specific insights?

Later, we need to grapple with crafting a message that says what needs to be said in a way that encourages the hearer to listen, to suspend disbelief, to engage. And we need to put it all in the context of a brand and channel that resonate with our target.

Again, do you want to craft your map by calculating statistics or by shining a laser into the crevasses of your target's soul?

Everyone is a free agent, now more than ever. Your target audience isn't going to do anything unless it's in their interest. Our job isn't to create products, it's to create demand, and that's a whole other kettle of cod. Who is likely to be motivated if you think of them as statistics and bundles of behaviors?

10C. "The consumer made me do it"

Oh, really? Which one? It's nice that you've chosen a target, and it's great that you've homed in on insights and used them to drive strategy and tactics, but you're going to be in a world of pain if you think of your target as "the consumer":

• First, that consumer doesn't exist. (I just drove around Denver looking for "middle-income female 25-54," but I couldn't find her anywhere. Instead, the streets were jammed with thousands of unique people. A more fruitful approach than assuming there is a homogenous mass of consumers is the one that identifies segments with common needs relative to your market and then attempts to profile the bull's-eye at the heart of each segment. They don't have to be fully representative of the whole group, but they do have to seem real.
• Second, even if you could find that homogenous mass of consumers, why would you assume they'll believe tomorrow what they believe today?

Mazel tov on selecting a target and investing in developing insights, but you're still on the hook. You need to stay in relationship with that target, with all her specifics and changeability. And know this: Once you've selected your dance partner, you lead. You are responsible and accountable for every decision you make. She may have said something in a focus group, but you're the one who decided to believe her and act on it.

11. "The numbers made me do it"

Numbers, it turns out, are just numbers. Data are just data. Who knew?

Numbers can describe what happened in the past with some degree of accuracy, and they can be used to construct models of what might happen in the future. But the responsibility and accountability belong to you.

The Coca-Cola Company had reams of data that "told" it to launch New Coke. That was true for Ford and the Edsel. Or back in the '80s when Apple CEO Steve Jobs insisted that Apple's business model of keeping everything in-house would be more successful than Microsoft's inexpensive licenses.

We're all going to make mistakes, and it's reassuring that numbers and models can help mitigate risk. But to assume they are Truth vs. a reflection of underlying assumptions suggests you slept through your statistics classes.

Nothing is as cut-and-dried as it seems. Back in the '60s, the marketers at Texas Instruments could have taken their cost-of-goods numbers at face value. Instead they asked what-if questions.

Then they went to market with prices based on what costs would come down to if enough units could be sold. It was daring. It was bold. It was marketing without hiding behind numbers—and it worked.

12. "Our thing does more things than their thing"

Engineers make features. Consumers buy benefits. Whose side are you on?

Strategy—your game plan for winning—must partner with insight into the mind, lifestyle, and needs of consumers Their offspring must then be crafted into a message. If your message is a list of benefits, go back to the beginning.

Ask yourself which you would rather buy: (1) an enclosure on four wheels, controlled by a steering device and powered by an engine, designed in Germany, with comfortable seats, a sound system, and devices for aiding visibility in bad weather or (2) the ultimate driving machine.

13. "Trust me, I'm an expert"

We all know better, and we all act as if we don't: We are not the consumer. Of course we don't want to be slaves to data (see No. 11), and of course we want to avoid paralysis by analysis, but the era of "trust me" should have ended before many of today's marketers were born. Be open to input from any direction and any source.

Think about what you know today that you didn't know two years ago. If the answer is "nothing," then you're lumbering down Dinosaur Lane; if the answer is "some useful things about Twitter," then consider what you might know in a few years that you don't know now. Take off your guru hat. Someone, somewhere, knows something you don't about each of your top five projects.

Each of us misperceives reality most of the time. If you're so caught up in your identity as an expert and you're not open to being influenced by the people you're trying to influence, then you will compound error with error. Cultivate humility.

Invest in building and refining your expertise. Think of yourself as a learner rather than a knower. If you are not growing, you're just another wasting asset.

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So there you have it. Mistakes to avoid. Not a new idea in the bunch. But then, there's a reason folks go to church on Sunday. The good stuff is so easy to forget.