While having technical difficulties, the lecturer for Intro to TV distracted us by making this up on the spot. Kudos to him for the effort. The following is my recreation of his anecdote because I can’t remember his exact words.
I should point out that this is in an ideal situation. We shall assume that the Armed Person is a man for the sake of simplicity.
There are two things that must happen for a grenade to detonate. The first is that the pin must be pulled. Second, a pressure switch must not have pressure on it. Therefore, the first step in disarming a man armed with a hand grenade is to keep his hand on the grenade! This is done by holding his hand upon said explosive.
Once his hands cannot detach from the grenade (thus disabling the explosive mechanism temporarily), you are to trip this man by knocking his feet out from under him. While he is on the ground, one of two things can happen. If you are a big, strong or both big and strong, you may stomp on him until he stops moving. In the case of smaller people (like me), you are to continuously fall on his neck until he stops moving. Josh recommends using the knee since it is a joint, probably bony, and a handy weapon in the situation.
With his hand still firmly held around the grenade by yours, and immobile, this is the prime moment to take the grenade into your own hands --- quite literally. Very carefully, scoop the grenade from his hand to yours. Make sure that the pressure pin is still locked down so it not explode on you.
If you can locate the pin, find it and put it back inside the grenade. The grenade now will not explode on you.
In the case the pin cannot be found, there is no other way to disable the grenade than just letting it explode. Placement of the grenade is vital depending on the surrounding area. If you find yourself in the woods or another rural area people are not likely to wander about, you are free to toss the grenade and allow it to freely explode. This begs the question as to why you had to disarm the armed man in the first place.
The more likely situation is that you in a populated area like a city or school playground. In this situation, the grenade must be placed in an area where it will safely explode without any casualties or injuries. You may think that a garbage can is a good spot for it, but THIS IS NOT THE CASE! In fact, the garbage can is a dangerous thing as placing a grenade in one automatically makes it into a shrapnel bomb. Instead, place the grenade under the immovable body of the formerly-armed man and advise everyone to run away. The blow of the grenade is stifled by the body, and everyone in the area is now safe thanks to you.
But you should really thank me for informing you on the process in the first place.