In order of spoilerishness:
You first have to figure out the controls yourself
Listen carefully to what Max says in reply to what you say
Try using wrong answers
So left foot gun would become right hand bacon for example
Do this correct 3x in a row and the room will flood with radiation, now you can send Sal in.
Sam: "We're 98% certain General Skun-ka'pe is evil."
Stinky: "And the other 2%?"
Max: "That he's crazy and we have to shoot him! But that may be wishful thinking on our part."
(Any resemblance to KOTOR is purely coincidential, really!)