To make the sign for hungry, take your hand and make it into a 'C' shape with your palm facing the center of your body. Start with your 'C' hand around your neck and move it down towards your stomach. The sign is a lot like food going down into your stomach.
We teach this sign by making it before feeding the baby, especially during times when the baby is acting like they are hungry and getting fussy so the baby associates hungry with wanting food.
This is a sign we like to introduce early on. By equipping our babies to sign hungry, they will be able to approach us with their needs instead of getting grumpy.