Manners is something that we all need every day.
Being polite and courteous means to consider the feelings of others. If we expect others to be courteous to us, we need to be the same. We must teach our children what is polite and what is not. A good rule to teach them is 'Do unto others as you would have others do to you'. A child's manners is a reflection on their parents.
One of the valuable qualities is to teach them to be sensitive to others and showing respect for others and cares about them.
A small child can learn to say 'please' and 'thank you'.
They may not always understand the true meaning, but the social part has been introduced to them. When asking the child for something us the word please with them and when you receive what you had asked for, us the word 'thank you'. The child will learn to say these words when their parents say them a LOT. When the child reaches the age 2 to 4, it is a great time that your little one hears the words, please, thank you, excuse me, and your welcome by you as their parents, but do not make a big deal if the child makes by overreacting . Just kneel down beside them, touch them and speak to them in a quiet voice. Lots of praise for good behavior goes a long way.
Table manners is another must for the child to learn. We as parents again can be an example to them and have patience.
Chew with the mouth closed
Elbows off the table
Don't complain about the food
Take small bites
Use please and thank you
Use indoor voice - no yelling
Wait your turn to speak
Use a napkin
When finished eating take dishes to the sink
Lots of praise for good behavior goes a long way.