He showed up <5 min late; I was impressed. I wasn't really worried about it; another guy, who's responded to my ads in the past, was waiting in the wings in case #1 bailed on me. I told him I'll be hatching a new batch in the Spring, and would undoubtedly have extra cockerels to get rid of, so he might want to be on the lookout for my next ad.
I got tired of being stood up a long time ago. I'll wait on someone for an extra half hour; beyond that, if they haven't called, they're just plain lucky if I'm still around.
I asked anyone I was meeting to buy birds to text me when they were 20 minutes away from meeting point. Only when they texted did I put any birds in the car.
This also seemed to reduce the no show rate overall. Maybe giving them a time meant they needed to make an actual plan with a time line which made the transaction more real than if they were going to meet me at the house.