The premise is pretty simple:
1) Go to post a comment.
2) Before you type anything, click the "Random icon" button.
3) This is now your icon. This is the expression your character has. This is what she is wearing. This is what he has in his mouth. This is what is happening.
3) Your tag must now be based on the icon.
4) Reply to others, always choosing a random icon first.
5) Let the hijinks occur!
Note: As the poster of this meme, I have no problems with nsfw icons, and in fact think they can add to instruction #5. Just give your threadmates a little warning for a happy and healthy meme-ing experience.