In his new book, "Quench Your Own Thirst: Business Lessons Learned Over a Beer or Two," Jim Koch tells the rollicking, often profane tale of how he built the  Boston Beer Company (home of Samuel Adams) and made non-imported lagers safe for discriminating drinkers. The following is an edited excerpt. 

I've learned a lot from my customers. Perhaps this comes from listening to them first and trying to understand their business before trying to sell them anything. I'm particularly grateful to the owner of Kappy's, a big liquor store in Boston. In the early days of Sam Adams, I went into his store to see if I could persuade the owner that carrying Samuel Adams would be good for his business. I was expecting a tough sell, but he immediately agreed he should have my beer in his store. Then he told me he had one very important request. He noticed that my best deal was on a twenty-five-case order. He asked if I would give him seventy-five cents a case off that price if he ordered fifty cases.

He said, "I'll give you a prime spot, and I'll call in my orders so you won't have to come back every week." I calculated that it cost me about $25 to make a delivery and about $15 to make a sales call. I did the quick math; he would save me forty bucks, and I'd give him back $37.50. I agreed immediately, since I would be making a little more money with him and anyone else who moved up to the larger quantity.

I then asked him why the seventy-five cents a case was so important, especially since he was selling a case for an eight-dollar profit. He smiled, as if he had been waiting for that question. "You don't understand my business. I have the best prices and expensive rent, but I still make more money than my competition. Young man, I don't make my money when I sell the goods, I make my profit when I buy the goods. That seventy-five cents is my profit."

I had never thought about business that way, but he was right. I had been so focused on making and selling my beer, I hadn't thought about the rest of the equation. At that point, I was making something like 10 percent profit on my sales. Sixty-five percent of revenue went into the cost of the packaged beer, and my other costs were about 25 percent, so there was 10 percent left.

I decided to look at every place we spent money. I found money everywhere! It was like opening all the drawers in your house and finding a pile of cash in every one. Occasionally, it was as simple as asking for a lower price. Usually, it required that I be a better customer. For example, I had sixty-day terms with our contract brewery because I needed the extra time to pay, but once we were profitable, I asked for and got a 5 percent lower price by paying in five days. I found a way to use lighter-weight bottles of equal strength, and that saved 15 percent on bottles. We got our wholesalers to contribute twenty-five cents a case to help support the salespeople we put in their market. The list went on and on, and a year later we were making twenty cents on every dollar of sales. By learning to make money when we bought the goods, we doubled our profit.

Excerpted from QUENCH YOUR OWN THIRST: Business Lessons Learned Over a Beer or Two. Copyright © 2016 by Jim Koch. Excerpted by permission of Flatiron Books, a division of Macmillan Publishers. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.