You’ve probably heard—and followed—a lot of sales advice over the years. And you’ve probably learned, maybe the hard way, that some of it is better than others.

But there’s one important component to selling that’s frequently overlooked entirely. It may even be the single most important part of a successful sales process. And it all boils down to one word.

Trust.

If a customer doesn’t trust you (and, in turn, the product or service you’re selling), he or she won’t buy it. It’s just that simple. Similarly, even after a sale, if trust is broken and never re-established, you have lost that customer forever.

What does this mean, exactly?

Have you ever sat through a pitch or presentation where a speaker from your company is describing one of your company’s products in a way that makes it sound just about perfect? You know the product has faults and problems, but there is no mention of these. You almost start to think, “Gee, I don’t recognize that product; I wonder which company makes it?”

If something sounds too good to be true, it generally is. And customers know this, even if they don’t tell you in so many words that they think you’re trying to pull the wool over their eyes. They just won’t buy from you.

So, am I saying you should tell the customer that your product is not perfect, and the reasons why? That maybe it’s not right for them at all? That you should go so far as to actively discourage the sale in some cases?

Yes. That’s exactly what I’m saying.

Hear me out: Customers already know that your product isn’t perfect (because nothing is), and that it’s not for everyone (because nothing is). Why pretend otherwise?

Tell the customer up front who the product is and is not for. What problems it solves and/or results it can deliver—and what it can’t do. You’ll instantly establish credibility because few if any of your competitors will be this straightforward.

Ironically, when you’re open about what something can’t do, people are far more likely to believe your statements about what it can do. And that’s how you build trust and credibility.

When a customer asks you in an initial conversation why they should buy your product, here’s how I suggest you answer:

“I’m not sure you should. We don’t know enough yet about your business to say that our product is the best for you. In fact, if you’re looking for the lowest price or basic specs, we’re almost certainly not right for you. That’s what we’re here to find out. Having said that, we’re very good at solving etch uniformity problems [you can prove this, right?], and our cost of ownership is generally the lowest. Knowing that, how would you like to proceed?”

In almost every case, the customer will want to proceed, which means you can now have a real conversation like you’re real people working together. A true partnership, in other words, instead of a warily adversarial, possibly one-time transaction.

And even if they don’t want to proceed right now, they will always remember that you treated them with respect and candor. Which means that if they ever do need the sort of thing you provide, who do you think they’ll call first?

Transparent honesty is so rare in today’s world that it’s like gold. Once you establish a real baseline of trust with your customer, and demonstrate that you can help solve their problems, they will be in your corner for life.

And you can bank on that.