Re: How do you slip the jab?
If you wait for the jab before slipping it, then you're one step behind the other guy. But if you're moving your head side-to-side and changing your height constantly, then you're making the opponent look for you. Then he will be one step behind. He will be jabbing where your head was just an instant ago.
But remember, don't fall into a head movement pattern. Keep it irregular.
Also, slipping the jab to the outside is always safer then slipping to the inside. For instance, against a fellow orthodox fighter, your main slip will want to be to the right. It's safer because, if you slip to the left (inside) constantly, then he can feint you with a jab and nail you flush with a right as you will be kind of squared up. But if you slip to the right, and he feints the jab, you can still easily slip the right by rolling or ducking to the right again.