A.B.
I started teaching my 5yr old sign when she was about 1. I started with things like eat....drink...baby...car...stuff that she could relate to.Look for books with easy illistrations. ASL is the most common(American Sign Language)ASL was easier for me and my little one than Signed English.Be careful though and make sure you speak english also for whatever they ask for because they can get lazy and have speech delays.