Most people are not even aware of what manners they should be keeping in mind and that is the main reason why they are unable to act in a proper manner. There is a distinct difference between those people who have good table manners and those who do not.
No matter how educated you are, if your manners are not good, then sadly no one will be able to respect you.
Some of the table manners tips are..
Saying please and thank you at the table
Saying Grace before meals
Not having elbows at the table
Maintaining a proper body language
Chewing with ones mouth closed
Not getting up till everyone has finished eating
Use your napkin properly