I used Baby Signs with my son but it doesn't matter what book or videos you use. You just want to use signs that your son can easily make given his dexterity level and you want words for things that are important to your son. My son stopped signing when he started talking so I think agonising over ASL or Baby Signs or whatever isn't worth it unless you are going to learn sign language and continue to use it once your DS can talk. Sign language for the deaf has its own grammar and syntax so it is really a language. I agree with pinky. Pick 5-10 words a week, make up or find a sign for each that is meaningful to you, write it down and use that sign with the word in conversations every day-preferably at least 5 times a day. It doesn't matter whether "bunny" is 2 hands on your head or wriggling your nose with one finger or moving your hand in a hopping motion with 2 fingers up. Great first signs are eat, cup, more, outside, hat. Most importantly, have fun! It is so much fun communicating.