Heinrich Schliemann, the archaeologist who discovered the site of Troy, had a great way of assessing employees. When he felt he'd found someone he wanted to hire for his historic archaeological dig, he took them out for lunch. This wasn't generosity or celebration; it was a test. When the food arrived, he waited to see whether the candidate reached for the salt and pepper before tasting it. If so, the job was off. Schliemann only wanted to work with people who investigated before making decisions.
I don't follow Schliemann's example exactly, but use my own variation of it. Eating with colleagues or clients, I watch to see who thanks the server when offered water, bread, wine--or when the food arrives or is taken away. The people who ignore the wait staff get my lowest marks because they exude a sense of entitlement, as though somehow they deserve to be served. The people who say "thank you" after each offer are the ones who get my attention and my vote.
I recognize that in some, especially expensive, restaurants, service can be so lavish that saying thank you at each offer would kill conversation. So I cut my subjects some slack. But the reason that I watch is because those who never acknowledge the people who work for them are people nobody would want to work for. Making those around you feel invisible is the opposite of leadership. On the other hand, noticing everyone and making them feel valued--well, who wouldn't want to work with that?
Even if lunch isn't feasible, see what happens when candidates are brought coffee, water, or juice. Find out how they treat your personal assistant or receptionist. All businesses and jobs depend on a vast number of people, often unnoticed and unthanked, without which nothing really gets done. They are all human and deserve respect and gratitude. That's the baseline.
But many people, even in low-level jobs, can do so much more. You also have to notice--and be grateful for them--if you want to bring out their best talents.