1. The most common way:
* Make a "C" handshape with your dominant hand (like you're holding a cup)
* Touch the tip of your nose with the "C" handshape
* Move your hand down and away from your nose, as if you're pouring the milk
2. A more literal way:
* Make a "M" handshape with your dominant hand (index finger and thumb extended, other fingers closed)
* Touch your chin with the "M" handshape
* Move your hand away from your chin, as if you're "milking" a cow
Both methods are accepted, and the best way to learn how to sign "milk" is to watch videos from a reliable ASL source and practice!