I couldn't agree more with Scott Hanselman's recommendation for teaching your baby sign language early on. I'm often preaching to friends and colleagues who are expecting their first child that they should look into it as soon as possible. Anyway, his post solicits feedback and thoughts from other parents, so here's our story...
When our older daughter (now nearly seven) was still a bun in the oven, we received the book Baby Signs as a gift. It's a fairly quick read and makes a convincing case that a baby's motor skills are capable of making basic signs much sooner than they're capable of speaking those words. The book suggests starting off with simple words, such as "eat" and "more," and introducing them when your baby's about 8-10 months old. They warn that you'll typically not see any response from your baby until their first birthday (or later).
Convinced, we gave it a go around the 9 month mark... and seeing her use her first sign (for "eat") just before her first birthday remains one of my proudest and happiest "Daddy Moments". Success begets success -- so once that first one was working out and she saw some results (i.e., we provided food when she signed "eat"), additional words were added to the repertoire fairly quickly. We quickly added "more", "please", "drink", "sleep", and "book". I find it interesting that Scott reports that his son, Zenzo, picked up the signs for physical things (light, fan) more quickly than abstract things like needs (eat, drink). His experience sounds like others I've read, where introducing the signs earlier than the book we read suggests can lead to earlier results.
In any case, there's not an ounce of doubt in my mind that a baby that learns to sign early on is a much happier and more content baby. A non-trivial amount of a baby's crying and fussiness is due to frustration over her needs not being met -- "you're just not getting it, people... I have needs!". Without any ability to communicate, you're left to guess at what has the baby upset. So if your baby has the ability to express her needs to you, a lot of that frustration is resolved.
Currently, we're using signs with our second daughter (now 17 months) and she uses all the signs mentioned above, plus a few others. She's also shown us recently that she really "gets" the notion of requesting things with her hands: she came up with her own invention for "music." It calls for both hands in the air with the hands making a finger-snapping motion... sometimes, there's bouncing involved or one hand pointing at the stereo. It's nothing like the ASL sign for music, but we get the point.
It's also very cool to have a baby that tells us when she's ready for bed (usually before the time we'd have otherwise put her to bed). If she starts to get a little fussy around 7-7:30pm, we'll ask her if she's ready to "go night-night". Usually, we'll get the sleep sign in return. She lays down and rolls over to sleep without a whimper.
As Scott mentions, there are some who worry that teaching a baby sign language may slow their progress in learning to speak. That hasn't been our experience... while it's anecdotal and the sample size is two, both girls began to speak simple words and sounds at around the same time has other kids their age. I was asked a couple of times by strangers whether our daughter was deaf or had hearing problems. When I'd explain that we were simply teaching her sign language so she could communicate with us, I'd usually get a look like I was nuts. Can't argue with results, though.
My only real regret around implementing baby signs is that we didn't stick with it with Allie (the older). Had we continued to add signs after she began speaking, she (and we) would probably be fairly fluent. We certainly planned to (and this was the reason we opted for ASL in lieu of coming up with basic signs on our own), but it just fell to the wayside. Thankfully, doing the signs again now with our second daughter gives us an opportunity to stick with it as a family. Allie and I have even talked about taking a weekend signing class together at some point.
So... give it a shot. It really is as simple as getting a sign language dictionary to keep handy, picking some basic words to start with, and then using the signs each time you say the word.