The "Harlem Shake" is performed by acting "normal" in the first 10 seconds of a video and after the first 10 seconds , you're doing random acts that makes you look like a primitive fool.
One example of the Harlem Shake is a young black male jerking off in front of what looks to be his parents who seemed to be reading a newspaper in the first 10 seconds of the video, not noticing their son is about to make a complete fool of himself. While this is happening, you'll hear a generic, goofy tune in the background. That's the start of the dance tune. 10 seconds later the tune cuts off to a deep voice, "Do the Harlem Shake," the video then cuts to a scene where his parents are gone but the same room is filled with what seems to be his friends in costumes. One of his friends is humping a stuff animal who is dressed in a cow costume and another seems to be jumping on a chair who is dressed in a costume that is unrecognizable. There is another friend of his dancing behind him who is also dressed in a white costume that looks like a bunny suit and a random white male walks in front of the camera for the sake of diversity. The man mentioned earlier who was jerking off in front of his parents in the first 10 seconds of the video is now dressed in a purple costume, pouring milk on his head while staring into the camera as he pumps his pelvis in the second 10 seconds of the video.