First one must understand what is the buyer's reason for selling. He might want to retire, bleeding money, or possibly he wants to cash out. Owners have put their blood, sweat and tears into growing their business, so respect and acknowledge of their achievements are appreciated.
The owners take pride in their business so it's important to find out the real reason for the selling. In my case, I'm looking for someone to take the business to the next level when I retire. Sure the money is nice, but money alone won't get the sale. I'm looking for an energetic, bright person to take my passion and escalate it.
Both parties need to understand the motivation of the other. A deal will only happen if it's a win-win. To do this you need to ask open questions, such as, "You built this great business, why sell" . Why aren't you giving it to one of your children? What would it take to buy your business and carry along your mission? Don't hard sell, just talk it out. The owner will tell you how to buy his compasny and what objections, you need to overcome,

Best book I can recommend that will give you a lot more ideas than I ever could (Never Split the Difference by Chris Voss): redacted