How do you teach babies American Sign Language?

In the same fashion that babies learn how to speak. They start associating certain words/signs to a certain object. For example, if you were to sign “water” while being around water, over time, that child will learn to recognize that that certain sign means “water”. Deaf babies learn in the same way. It’s best if you start at a young age, since language learning is best at those times.

My sister taught her son sign language VERY early, before six months I believe. All she did was make the sign while saying the word. For example, she yould ask him, “Do you want some milk?” (saying the word milk slightly louder) and make the sign for milk before giving him any. He learned very quickly that if he wanted milk all he had to do was make the sign, and was able to be very clear about what he wanted. She did that with a few other signs (done, more, and dirty come to mind first, although there were several others.) By the time he was about one, he had replaced most of the signs with baby words, but still used his signs once in a while.

For a deaf child, it would probably be the same process, simply without the need of speaking. If you make the sign for milk immediately before breast feeding many times in a row, the baby will quickly learn that the sign means “milk” or “food.”