There are two types of salespeople: the effective ones and all the others. What separates the good from the bad? A few things, actually. When I meet the people who are coming close, but not quite hitting the mark, they’re usually making at least one of these mistakes.

Let’s start with the first, worst and most-common mistake: not listening to the customer. So many otherwise good salespeople are so focused on the end goal, so focused on the process, so focused on closing the deal that they tune out what the customer is saying. When customers tell you what they want, they’re doing you a huge favour. When you listen to them, you gain an understanding of their needs and problems. Only then can you position yourself as the solution.

Overselling: When you come on too strong, you run the risk of scaring off a potential customer.

Number three is a first cousin of number two: It is good to be persistent. It is not good to be annoying. When you pester someone or bombard them or demand an answer when they’ve asked for time to think, you become the person who triggers the “oh no, not you again” reaction every time you call. There is a fine line between being persistent and being annoying. Try to deliver the message right the first time.

Lack of preparation: Prepare to the point that you know every intricate detail of your customer’s overall industry, as well as of their specific business. You have to be able to speak authoritatively and present real solutions. Trying to sell to someone without understanding the processes and problems of their industry comes off as amateurish. Don’t bluff. If you don’t know the answer to something, say you don’t know. If you have to get back to them, say you’ll get back to them. People can spot a phony.

Relying on the infallibility of the process: Use the process as a guide, not an absolute. If your process doesn’t work with a specific person, ditch it and try another method until you get a good response.

Failure to understand the customer’s constraints and buying behaviour: When you know what is holding a customer back, you can adjust your strategy to make them comfortable with buying.

Failing to qualify a customer in or out of each different stage of the cycle: This one is difficult, but it might be the single defining characteristic that separates good salespeople from bad ones. In North America, specifically in the U.S., the process moves much more quickly than it does in the U.K., where customers spend far more time determining the ROI of anything that costs more than 40 pounds. In the U.S., people tend to be much more direct when it comes to saying no, where a salesperson is far more likely to be left dangling in the U.K.

Finally, know your audience and take the time to learn the cultural nuances that separate different buyers in different markets. In the U.K., for example, “no” often means “not now”—but if you don’t settle on a definite follow-up time, you can kiss the deal goodbye.

Trust your instincts, don’t annoy people, be prepared, know your audience, listen. The elements that make great salespeople shine sound like common sense, but you’d be surprised how often the most basic elements are overlooked. Figure out what to do by knowing what not to do.