[RStar]

I've always used the two shell shuffle, and find it both easy and non-messy. The other way I've seen others do it is through their fingers- messy and slimy. Though the water bottle trick is impressive when you have an audience!

Or if you need a lot of eggs seperated, you could crack them all in a big bowl, then seperate all of the egg yolks out in one step (emptying the single yolk out of the bottle each time, of course). Just make sure it's not a nasty spit infested water bottle full of germs!