How to Sign "Yeah"
To sign *yeah* or *yes*, start by making a fist with your dominant hand (an ASL 'S' handshape). Hold your hand up comfortably in front of your shoulder or chest. Keeping your arm relatively still, bend at your wrist to nod your fist up and down a few times. The motion should look exactly like a head nodding in agreement. Be sure to nod your actual head at the same time to naturally emphasize your confirmation.