I'm a sophomore in college now, and I vividly remember playing this game on the bus ride to and from school in elementary school. (Not the 64 version, although at camp we played that one too.) It was just 8 of us or so, in the Gifted and Talented Program, so we all got really close. Over the months we ended up making many variations on the original, using feathers to tickle people's backs, making it less gory with milk and cereal and bowls and spoons, etc. Our ending was also a LOT more detailed than most of the ones I've read about on these responses. The general formula is as follows:

[Person has their eyes closed and is relaxed, either sitting sideways on a chair or standing]
Chorus:
Con-cen-tra-tion
Con-cen-tra-tion
People are dy-ing
Children are cry-ing
Con-cen-tra-tion
Con-cen-tra-tion
[while firmly beating fists on the person's back to the beat of 4]

Crack an egg on your head [bump fist on head]
Let the yolk run down [x3] [trail spider fingers down back]
[Repeat]

Chorus

Stick a knife in your back [beat fist once against top middle of back]
Let the blood run down [x3] [spider fingers]
[Repeat]

Chorus

Insert variations here: (Crack bowl on head, milk run down; stick a fork in the back, let the meat/blood run down; stick a spoon in the back, let the milk/blood run down; put/kill a bird/chicken on your head, let the feathers run down)

Now, you're on the top of a taaaaaalllll skyscraper. [move head/torso around in a biggish circle]

You walk forward. [if standing, make person take two steps forward]
Suddenly, you hear footsteps! [clomp clomp clomp]
You look right [turn head to right]
You look left [" to left]
You look up [" up]
You look down [" down]
Nooooobody there. [shake head back and forth "no"]

[Repeat x2, each time getting more anxious that you can't find where the footsteps are coming from]

Gasp! You've reached the edge!
You leeeeeean over to get a better look, [bend person forward]
and [push person forward out of the blue!]

The color they see when they open their eyes represents how they died when the disembodied footsteps pushed them over the edge. When I happened to get a free pack of fake multi-colored feathers, we get creative and took a handfull, throwing it up into the air as the person is pushed. What they manage to catch also signified something about their death, although I can't remember what they all meant now.

Huh, now that I actually write this down, I realize how long this thing was, and how...er, creative we got. Innovative little buggers, weren't we? Maybe it's the G&T piece coming out a bit. Kids have some messed-up minds sometimes. (Really, blood, children crying and people dying?) makes me wonder where this actually started from and if it's something similar to the backstory for "Ring Around the Rosie".