<pedant> Bodies is by Drowning Pool </pedant>
<serious> OP was that in your bjj class or some kind of km grappling? In most bjj competitions daki age is banned and would be considered a dick move in rolling.
Lindz: It was a KM grappling course, although I doubt either of the legitimate BJJ instructors teaching out of my school would hesitate to teach that move (after telling us that it's banned in competition).
The KM instructor suggested that I shouldn't rely on it in any case and that I needed to learn how to pass the guard.
Underhook a leg with one arm, then slap his face with your free hand for being suck a dick.
The clue that he is going to pick you up and slam you is that he will grab both your collars. First of all if someone grabs both your collars you should be trying for an arm bar or other type of attack. However if you are are in a position that you can't stop him grabbing both collars and he starts lifitng you up you have two options, either open your legs and place your feet on his hips or underhook one of his legs which will take away his leverage to lift you.
My personal aversion to guard slamming as a way to get out of someone's guard is that it doesn't actually get you out of their goddamn guard. What's more, it can lead you deeper into the guys guard and make it easier for him to hit a sub/sweep after the slam. Hence, I believe, why yli called it a high risk move.
But learn to pass the guard by passing the guard. Slamming obviously works, but it works the same way stacking someone in their guard and punching them in the face works.