"Aviate, navigate, communicate ... in that order"
"Thumbs UP" -- when one grasps the stick (or yoke), extend the thumb up -- as one wipes the cockpit with the stick, the thumb will point to the wings and the aileron on that wing should be up -- just a check on the correctness of the rigging.
"Make sure your head and your a$$ are wired together before engine start"
"Don't ever run out of airspeed, altitude and ideas at the same time"
And finally, from, I'm told, the fighter pilot community, "Honor the threat!" If the other guy in your part of the sky is doing something incomprehensible, watch him like a hawk.