What are you supposed to do if you fart in front of a guy?

Well... if he doesn't hear it act like nothing happened. If he does hear it he'll look at you or say something. If he looks at you pretend to crack your knuckles and don't look at him. If he says something like "Did you just fart?" say no... don't yell NO!, because then you will sound embarrassed. Act casual. Also, say something like "I was just cracking my knuckles" or "No, my foot skidded across the floor and made a funny sound." Don't be embarrassed, because everybody farts, he will probably forget about it by tomorrow.