Must be taller than 4ft 11inches and willing to buy lunch.
On the more practical side, I would advise a buyer or seller to observe the agents reaction when their cell buzzes. Is this agent more interested in business they don't have or the business across the table?
How is starts portends how it will end.
Remember, dear buyer or seller, there are ONLY 5 questions you need answered and they must be answered without you ever asking them. THEN you Know.