In a true democracy everyone can be upper class and live in Connecticut.
Preppy clothes are built to last, since they certainly won't go out of style.
Always underdress. The goal is not to look as if you made an effort for the particular event. If you can dress for a different party (i.e., wear black tie to a cocktail party, or tennis clothes for lunch), so much the better. You give the impression of being much in demand.
Sarcasm mascarades as the Preppy's sense of humor.
Like everything else, Preppiness begins in the home.
A tip: if you're invited to your friend's country club to go the lost and found bin and pretend that you left something there. Next thing you know, you have a fabulous sweater.