Take note on how many cards does he have in his wallet, and does he like to keep coins?

I'm a guy here giving my opinion - these are the two aspects that greatly affects the type of wallet that I will buy. I carry a lot of cards, but I don't like to keep coins (so wallet with zip compartment I wont buy). I also would love those zip-able cash compartments - and finally I will find one that have 2 "ID" display section (one for IC one for license).

Just my two cents. Observe the guy's behaviour. I'm sure most guys wouldn't really mind if you wanted to take a look at their current wallet