When my son was about 20 months old, his most common sign, by far, and most helpful was the sign for HELP. We used a common modification to ASL to teach it. The real ASL sign is complicated and involves dropping the hand with fist clenched thumb extended upward onto the other hand and then raising both upwards together. This is hard for a baby to do and while a toddler might master it easier, a better sign was adapted. The modified baby sign for HELP is done simply by patting the chest with open palms.
After trying for some time to teach the real ASL version without success, I switched to the baby sign adapted version and my son took to it immediately. At first your baby is going to be pretty easy going and happy to just sit and watch what others are doing around him, but as he grows older and more capable he’ll want to join in. As he’s trying to get the hang of things his desires will outstrip his capabilities and this is where frustration will set in. This is the crucial time where you should take action and teach the sign.
So when you see that your baby is getting upset trying to do something teach the sign for HELP. Repeat it just as many times as you need to have it be associated with getting assistance. If you’re keen on teaching during this time frame, also teach the sign for FRUSTRATED which is done by bringing the back of the hand swiftly toward the face. Think about running your head into a brick wall as you do it! Your baby might move his open palm to his face rather than the back of his hand, but as long as you know what he’s saying, this is fine.
After both signs are fairly well understood, you’re going to want to break things down into a logical sequence. You want your baby to tell you 1) That he’s FRUSTRATED by signing it and 2) That he wants HELP. Remember that not all instances will warrant helping. There will be times when your baby and toddler will want to figure things out for themselves. This is the time to ask if your baby wants help. Other times you might want to offer help from afar, recognize your baby’s frustration and encourage him to work through it on his own. Being too attentive can create a dependency so be cautious. Stay just slightly behind your toddler, letting him lead the way through tasks so as to build his confidence. Breaking through previous milestones and tasks is what creates self esteem in children, not in general avoidance of frustration! Keep this in mind as you use these two very important toddler signs.