If you are unable to remember someone’s first name, simply ask them: “What’s your name?” When they reply with their first name, laugh and say “Oh no, I knew that, of course. I meant your last name”. This is a much more acceptable thing to forget–and you still get their full name.
— Bettina, from Tricks of the Trade: Socialite

This is brilliant, but what about when I forget this question?
Me: Who the hell are you again?
Them: What?
Me: Oh no, I knew that, of course. I meant your last name.
Them:  Go away!
Me: All right, I’ll talk to you later.
Me: *Writes down Wot Goway*