For good executives, it’s second nature to show appreciation toward clients and staff. But often, we overlook less obvious people who have made a difference in our professional lives. The other day, I was talking with a client about his growth plans for 2012 — which, he knew, would depend heavily on word-of-mouth. He wanted to strategize about cultivating new referral sources — but in the process, I realized a major chunk of his existing business was the result of one woman. A look of panic crossed his face: “I guess I’d better thank her.” Sending someone business is the highest compliment possible. Don’t throw away their goodwill by forgetting to acknowledge that trust. I have colleagues who — years later — seethe about people they helped who never acknowledged it.