Stopping a kid from throwing tantrum or meltdown needs preparation ahead of time, patiences, positive attitudes, and most important, ideas.
For example, before you can talk to a screaming kid, you should first distract the kid so that your kid will listen to you. If you see a flower nearby, you may say "Look, that flower is so beautiful!" Or if you are trying to stop your kid from running, and there is nothing else interesting at the moment, you may say "Let's make a train to go into the store! It is much more fun than just running!" or "Let's play a game called Who can Keep Quiet. People who makes sound first loses."
Always being positive and save the punishments to the end when you really have nothing else to try. In this way, children will be more open to you. Use words like "A great boy/girl will never run and scream in public. You are a great boy/girl. Do you know what to do?" as much as possible. Besides, praising your kids whenever they make improvements is another way to be positive.
Here are some ways to communicate with children on their behaviors:
Way 1: Most commonly, setting up rules to earn rewards ahead of time.
Two steps to set up a goal ahead of time.
Step 1: Find a reward really matters to your child. Use the things you child really like as the reward. Besides, DO NOT offer anything children cannot get in daily life such as lots of candies or long screen/video game time in one day as the reward. For example, if your child has animal crackers as afternoon snack, you can say "You have grown up, not a baby anymore, so you need to behave to earn your own snack". Suitable rewards include healthy snacks, high quality chocolates, and even interesting workbooks. Try avoiding words like "If you don't behavior well, you cannot get your afternoon snack."
Step 2: Step up rules. For example, behaving well in public for the whole week/day is the way to earn the reward. Let your child join the process of setting up. If your child think one week is too long, and would like to shorten it to two days, you may agree or disagree his/her ideas, and give out the reasons. Reaching the final decisions with your child will make the rules easier to be followed. After setting up the rules, DO NOT change frequently, otherwise your child will be confused.
Way 2: Reinforce positive behaviors.
Reminder kids what they did in the past and how they did well.
First, mention things like "Remember last time you kept quiet in this library and the librarian praised you? So please do the same thing this time and people will like you." or "Do you remember three days ago your teacher gave you a sticker for being polite to her? See, being polite is a good thing and I believe that you understand it and will keep on doing it."
Second, mention the details of good behaviors, that means reminding kids why and how they did well in the past. Try to describe the details as much as possible. For example, you may say "You were very excited to see so many candies in this shop and wanted to buy a whole bag of them last week. When I told you that you could only buy two candies, you did not cry or scream, but talked to me peacefully for buying more in the future. That was very good of you to self control. Today we are going to an ice cream shop, would you please do the same thing? You can pick any two flavors, and we can taste other flavors next time." In this way, kids can understand your expectations clearly, and will not get confused on what are the good behaviors vs. bad ones.
way 3: Point out the consequences in details.
This means giving children clear ideas on what bad behaviors can cost them. Try to use detailed consequences instead of vague ones. For example, instead of saying "You will get a big punishment if you do not stop running and screaming", you may say "It is easy to hit others if you run too fast in a place full of people, and your screaming could interrupt others' conversations. As a result, people will think you as a rude kid, and you will be driven out of this place/ I have to take you home immediately." It is difficult for kids to understand what a "big punishment" is, but much easier to understand people will not like him/her if he/she runs and screams in public, plus he/she will be taken home and cannot play anymore.
Way 4: Express your trust to kids of being great and ask them not to lose your trust.
Building trust between parents and children is a long term hard working. After you explain the differences between good and bad behaviors, add something like "I trust you will be a great boy/girl by not throwing tantrum in public. Do you want to keep my trust?" Repeat the word "trust" from time to time, and set up one/multiple symbols of trust. Anything can be the symbols such as a trust hand/finger, a car key, or even a toy. Use the things you will carry wherever you go with kids, since you may need the symbols anytime handling kids' meltdowns. You may say " After you run very fast and hit another kid last time, you promised me that you would not run that fast in this playground anymore. I trust you will not do it this time. Here is my trust hand/finger, do you want to hold it and keep your promise?" If kids say no, it is OK to try more times since building trust with kids needs time.
Way 5: Ask children to express themselves on what make them so excited or why they behave badly.
Usually when a kid gets very hyper in public, there is a reason. The important thing is to find the reason and solve the problem. You have to wait for kids being less excited/finish screaming or distract kids before asking questions. Keeping your own voice low and calm, of course, being patient at the same time, ask your child whether there is anything interesting or or there is any other reason.
For example, you may ask "Great, you are not screaming anymore. Do you still remember why you were so excited and screaming & running in the crowd?" Your kid may not be willing to tell you at this moment. Do not give up, and ask yes/no questions instead, which are easier for your child to answer. You may ask "Did you see anything new?" or "Did you just run after that kid so that you can play with him?" or "Were you chasing that bird?" Try as many options as possible until your child says yes.
After finding the problem, it is important to choose a positive way to solve the problem. For example, if the problem is that your kid sees too many people at the same time, which is common, you may say "Do you know what kind of kids they will love? Polite kids! Polite kids will not screaming and interrupt others! Polite kids will not run very fast in the crowd and hit others! Do you want to be a polite kid?"
Sometimes kids get angry with siblings at home because they want to play the same toy at the same time, or one kid plays the other kid's toy. You may divert their attentions by saying "Do you think playing this lego set is really important? We have lots of other lego sets, and you can play any of them. Besides, great kids share with friends. Please take turns, and you can discuss about how long each of you play with this set. Do not forget to set up a timer." Encouraging kids to solve problems by themselves is way better than ordering them following certain rules.
Way 6: Using imagination friends as role models.
Believe it or not, imagination friends are more effective than real friends. The reason is that you can use imagination friends in any case without being questioned.
Before using imagination friend(s), you may have to set the character(s) up first. For example, if you tell your child that Mike is doing homework faster and better than him/her, you may get questions like "Who is Mike?", "Where does he live?", and "How do you know that?" These questions are easy to answer. You may answer "Mike is my friend's son. He lives 20 miles away. His dad/mom tells me that." After introducing the imagination friend(s), you can explain why Mike is faster. You may say "Mike is very focused on the homework so that he has already finish his homework. If you want to be fast, focus on the work now, instead of staring at that bird in the yard!"
You may set up more that one imagination friend for other purposes. Fo example, if you want to praise your child's improvement, create another imagination friend who is not as good as your child. You may say "John is not as fast as you. He is still doing homework and you have already finished. However, he is trying hard and improving himself. He said he will work as hard as possible and want to do the homework as fast as you. Do you want to lay back and not work hard anymore?" Children like being good, and they will be encouraged in this way.