Step 1: Materials
Two or three strands of yarn
(This means you'll need two to three balls of yarn of any colors)
And, of course, your arms!
Step 2: Casting On
Grab the working yarn with your left hand (the right if you are a lefty) and with your thumb go over the working yarn (while still holding it in hand) and up (like in pictures) then with the two fingers closest to your thumb grab the tail so it looks like in the picture.
Slip your hand between the working yarn on your thumb over and through the tail on your other fingers and back through the working yarn (look at pictures) and tighten around your wrist. Do this same thing about 11 more times until you have twelve stitches on your wrist.