If your child is already signing back to you, try learning some signs for specific things he really enjoys. For Nate, WASHING MACHINE and VACUUM were big early hits.
While Nate is making the sign for pancake by clapping his hands together vertically (an approximation), the ASL sign is actually more horizontal. Click here to see. Babies often perform signs a little differently, especially when they are younger and their motor skills aren't as developed. Caregivers should continue to make the sign correctly and in time, the baby will likely perform the sign more accurately as well (just like with verbal speech).
What were some of your baby's first signs?
If you are new to baby sign language or want to know more, you should check out my baby sign language page here. I also recommend Baby Signing 1-2-3: The Easy-to-Use Illustrated Guide for Every Stage and Every Age.