The number one rule in martial arts is that the number one rule changes with the situation and whether or not there are rules...

Keep your eyes on your opponent.

Dig in

"90 percent of karate is half mental."

"The enemy is always bigger, faster, and stronger than you are."

"Posture is everything."

"Always picture a straight line extending forward from your feet, and stretching off into infinity. Why infinity? Because that's how long it will take you to get the stance right."

And this, while not strictly a rule, was the one of funniest things I've ever seen in the dojo.

Sensei: Is your gi on backwards?
My sister: Ossu Sensei
Sensei: Well then, I guess you'll just have to the kata backwards.

He made the entire class do the kata backwards. Twice.

Let's see here...rule #1's that I've heard...

#1 - Don't get hit (we're talking Aikido here)
#1(a) - Don't forget to breathe
#1(b) - You can't move your hips without moving your feet
#1(c) - Your other hand should be doing something

Actually, the last one isn't so much of a rule as it is what he says as he's pointing out WHY that hand should have been doing something else (ouch).

The block is the most important thing

Get your hand in the cave...(you all know that term, ?.. means have other hand always read to use, cocked back...)

Never play cards with anyone named "Doc."

Never play pool with anyone named "Slim."

Never sleep with anyone crazier than you are.

Never say that size is not important.

Knowing MA is good, but it always helps to be in greater numbers.

-Taison out