Twenty years ago, I found my mechanic—Victor at Yuki Imports in Los Angeles—via a referral. Since then, I've recommended him to countless friends and colleagues, and I couldn't help but laugh when I saw a sign in his waiting room that asked customers not to write positive reviews on sites such as Yelp. The shop was overbooked with customers, the sign explained, and it couldn't handle the influx of new customers.

That's a nice problem to have. And it might be yours, as well, if you follow some of Victor's best-practices.

1. Do a good job for a fair price

Would you recommend someone who does a so-so job that costs more than it should? Any word-of-mouth recommendation rests on a quality product or service that offers good value. Victor's work has never disappointed me, and the final tab is usually lower than his very reasonable estimates.

2. Be trustworthy

Recently, I became convinced that my car's brakes needed a complete overhaul: rotors, calipers, the works. And that's exactly what I told Victor as I handed him my keys. Imagine my surprise when he called to say my brakes were actually fine: the pads were still 50% at the front and 90% at the rear. He didn't try to sell me something, even when I announced I needed it.

3. Look out for the best interests of your customers

When we take our car to the mechanic, we all know what's coming: a list of other things—usually expensive—that should be replaced or fixed. Victor is like any other mechanic in that regard, but he explains what's important, what can wait, and what might be covered under a manufacturer's warranty.

4. Amaze your customers with service beyond their expectations

Last spring, I dropped my car off for scheduled maintenance and told Victor to do anything else that needed doing—up to $1,000 total—without asking for approval. A few hours later, I missed his follow-up call about a new radiator that would push my bill over the limit. He put the radiator in anyhow, with the explanation that I was a good customer, my car needed the radiator, and he was willing to risk my refusing to pay for it. (I paid for it, of course.)