I find the gate signposts a little confusing at IST when connecting. There's a long hallway with some gates requiring pax to take a parallel ramp at the side. I had to doubleback a couple of times so I now I pay close attention to the signposts.

A quirk of IST: the display board will say "Wait in Lounge" when they are about to board. This does not mean the airport lounge but the gate area.

On the inbound return, remind him that he has to get a security sticker (they ask some canned questions for all US/UK bound pax) before he goes through transit security. There are signs pointing to this area, which is just before and opposite of the transit security area.