Children need to understand why it is important for them to have proper table manners and at any other time in their lives. Children are more likely to remember specific manners and etiquette when you give them a brief explanation of why a particular behavior is considered rude or rude.
Avoid giving long talks and telling stories with too much detail. Instead, it simply indicates the reason why a specific behavior cannot be appreciated. For example, if your child is chewing with his mouth open, say something like, "People don't want to see food in your mouth when you're trying to eat." In this way and with this indication, your child will realize that he should eat with his mouth closed and it will make this behavior conscious.
Tell your child calmly and objectively that with manners in mind, other people will appreciate your effort to have a good education at the table or in any other context.
Age-appropriate expectations
You also need to have age-appropriate expectations, because you can't expect great manners in 3-year-olds either. You have to make sure that your expectations are appropriate for your child's age and developmental level. You can start working with a young child on the basics like saying "please," "thank you," and "I'm sorry."
By the time your child is a teenager, you should focus on advanced skills like putting the phone away in social situations and more complex communication skills. Sometimes it helps to really focus on one area at a time, such as basic table manners, before moving on to other skills. If you demand a lot of learning from your child at once, they may become overwhelmed and not move forward. It's also common for skills to be reviewed from time to time to make sure your child remembers to use them.