Hi!
Here are some principles I've taken from the knife defence lessons we've incorporated into our classes from Instructor Ben Beard:
1, Have your hands up, don't let them grab your neck or clothing (otherwise they inhibit your movement) 2, Hurt them if possible when you make your first move (in order to stun them) 3, 'Clamp' their knife hand or arm under your elbow or wrist (so that they can't pull back to re-strike) 4, Be constantly moving while hurting them with elbows and kicks etc (in order to unbalance them and keep them uncomfortable) 5, Attack their thumb or little finger if they have a strong grip (in order to disarm them) Usually if they are 'showing' the knife it means they just want to rob you and not kill you - they will tend to conceal the knife if so. However you can never be sure, so it's always better to have techniques you've trained repeatedly at your disposal if you absolutely need to use them! Stay safe! -Sifu James JM Wing Chun