On final approach to the check-in counter...

AGENT: "Welcome, wxguy, how are you?"
WXGUY: "Tired and cranky."
AGENT: "Oh, sorry to hear that, how may I help you?"
WXGUY: "I'd appreciate a nice quiet room away from everything."
AGENT: (typety typety typety; crosses out pre-assigned room)

It usually works, thought not always! It has saved me from many return trips to the FD I'm sure.