It's amazing how quickly Donovan can pick things up when given the chance. Around his first birthday we've been using a bit of sign language to help with our communicating, and although he doesn't use that many signs, that's really something that is more my fault than his. Every time that I consistently use a sign over a couple days, and give him opportunities to use it himself, he picks it up right away. It's really, really cool. Just this past week he's learned to sign "open" (although his version is more him waving his hands in towards each other and then back out again) and he's kinda figuring out "hurt" as well.
Way before getting pregnant I remember hearing about using sign language with babies and toddlers and loving the idea. I tried to start several times when D was younger, but I didn't expect it to be so tough. Not so much the signs themselves, or even learning them, but just incorporating them into our days. Up until he was 1 and walking it seemed like my hands were always busy doing something else (like holding him) right at the times that I wanted to show him signs (many of which required 2 hands).
But then around his birthday I finally started getting more serious about it, and was rewarded pretty immediately. He quickly learned "more"(pic above), "water", "eat", and "all done." More has broadened in meaning so he uses it almost any time he wants us to do/repeat something (like reading a book again, or undoing the buckle he just clipped together so he can do it again), in addition to when he's eating. All done has also expanded to all situations, not just meal times. He knows that "water" is the same whether he's drinking it, watering the plants, or swimming in it, which is pretty darn cool if you ask me. Even just these few simple signs have been EXTREMELY useful in helping us figure out what he wants, and so even if you don't want to bother with any of the rest of it I think these are worth teaching to your kid.
Since then he's also learned "cat", "milk", "open", "hurt", "bath", and "toilet." Some signs take some figuring out before I realize what he's saying, but others are pretty spot-on. There's a couple schools of thought on what kinds of signs to use-- there are books called Baby Signs that have their own signs made up under the idea that ASL (American Sign Language) signs are too hard for babies to use, or they tell you to make up your own signs. I personally feel like that's kind of trying to re-invent the wheel, and have just chosen to use ASL signs in large part because they're so easy to find. I use this website often to look up words, and if they're not there usually a search on google for ASL and the word I'm looking for finds it for me. It's also nice that any of our friends or family who want to learn these signs can easily look them up, too. I know I'd never be able to remember signs I made up, and seems odd to have to go buy specific books to look up their made-up signs. Some signs are a bit difficult for D to make, but I recognize his version and keep signing the regular version back to him, the same as you do with speech. All that said, this is the system that works for me and that may not be true for everyone. As neat as it would be, I don't intend to keep teaching ASL to the point of fluency when he's older so the exact signs used are kinda arbitrary.
I keep trying to think of words that are useful to him on a daily basis that I can introduce signs for, like for specific foods he likes so he can ask for them (rather than just point to the kitchen when he wants something different than what's offered). He seems to really like itn when I show him a new sign, and tries to imitate it right away. I know some people think that teaching kids signs means they aren't motivated to talk, but I don't think that's the case with D. I think his verbal language is just developing at its own pace, and am grateful that he knows these signs so he can communicate with us in the meantime-- and it's reassuring to me to see him understanding and communicating this way, to know that his language development is going great even if he's not speaking much yet.