The most important thing I learned was to make sure you take your death rag off your head before starting another round (thanks for letting me know I still had this thing on guys, heh)
Interesting things I heard:
"Is she your girlfriend?"
"No, she's my daughter"
"Those are dummy rounds"
*pull a bullet out of one and find it's a live round*
"Damn, I paid extra for those"
"Where is the ammo dump?"
"You're standing in it"