Things to remember while planning a formal 21st party?!
Depends on your version of formal.
Music should be what most of the people invited like.
Food can be basically anything, but a formal dinner (or is this a diner where you are asking people to dressinlong gowns ans tuxedo) is usually, small beginning salad, appetizer, soup, main course, dessert. Usually includes wine.
Table setting include, salad fork, appetizer for dessert fork, main fork, Soup spoon, dessert tea spoon, App knife, main course knife.
There are many website that show how to set up the table