Start by teaching the baseball players a "key." Instruct all team members that when you touch your belt they should look for the baseball sign. The "key" can be any part of your body. The "key" tells the baseball player to pay attention because the actual sign is coming next. The "key" also prevents the opposing team from stealing your baseball signs.
Create a sign for hitting the ball. Let's say when you touch the top of your baseball cap you want the batter to swing. You will first touch the "key" (belt) and then touch you cap (hit). For younger baseball players, proceed slowly and give them an opportunity to ask you to repeat the sign if they do not understand.
Continue by adding other baseball signals, including ones that do not mean anything. For example, if you touch your nose, ear, mouth, belt and hat you just gave the hit sign. If a player forgets the sign, he should know that he can call time out, approach you as the coach and have you whisper the instructions in his ear.
Keep your signs simple. Young kids will have a hard time remembering the signs as it is. You don't need to confuse them even more by using 10 signals in an at-bat.
Create baseball signs for bunt, hit, take, steal, and hit and run. Remind your players that the key must be touched first for the sign to be active. Have your players help you make some of the more rarely used signs to build camaraderie and have some fun.
Give different signs to different kids to keep the opposing team guessing more. If one of your players has hard time remembering the bunt sign, change it for him to something he can easily remember, but leave it the same for everyone else.