Print out this template. (Click on the image)
Using the template, cut two rings out of some thin cardboard.
Start twisting wool around the rings of cardboard.
Go on until you can't see the cardboard anymore (and a bit longer).
Move some of the wool to reveal the cardboard.
Stick the scissors in from the side.
Cut trough all the wool and tie a little string of wool around it, between the two rings.
Remove the rings
Move it around a bit in your hands to make it a little ball.
Stick eyes on it.