We started trying sign language with the babies when they were about 6 months old. We weren't consistent with it, though, and we eventually stopped altogether.
Recently, I noticed that Vivienne can copy us very well, so I tried sign language again. This time, she picked it up immediately. She can say "more" and "all done." She not only uses these words when eating (which is very useful), but also in other situations, like when she is getting her diaper changed. She will sign "all done" to me over and over... more like "Mommy, PLEASE RELEASE ME!!!" Needless to say, neither of our babes is very enthralled by diaper changes these days. Miles flips around on the changing table like a fish out of water.
Vivienne and Miles can both show us where their heads are. We'll ask,"Where is your head?" and they will put both of their hands on their heads. This morning, I was asking Vivienne to point to her feet and her belly, and she was able to do both. We just taught her "foot" a few days ago. I think we should start trying to teach them more words for body parts. I can't wait to sing "Head, Shoulders, Knees & Toes" with them.