A prep can take on several forms, but it is most certainly not someone who shops at american eagle, hollister, areo, or abercrombie since 1970. Its a person who comes from a upper class, established family who dresses and lives in a conservative american style. I like to break the prep genre down into three classes:
1) Coastal Sea-farer: A person from an upper class family usually from the New England coast who enjoys boating (sailboats and yachts). Typically has attended a NE boarding school and private college, this education needed to handle their parents' fortune. Can be seen wearing vineyard vines, polo, lacoste, brooks brothers, and anything associated with sailing. When not on the water drives a Land Rover or Mercades. Lives on the coast but does not associate with beach bums or the surfing types, only with other sea-farer families. Family may be established in business, politics, or medicine. See the Kennedy family or the Cleary family from "Wedding Crashers"
2. Country Clubber: Person who can be found at the high end country clubs in most major american cities, though I believe they may be stronger in the south. Grow up at the local private school and wear polo, brooks brothers, lacoste, and other country club attire, drives a BMW. Lives in the high society of their community where the deb ball is more important than the prom and appearance is high on the list of priorities. Plays mostly golf and tennis, though they might suck at both.
3. Outdoorsy Prep: Someone who spends a lot of time outdoors engaging in outdoorsy activities. May draw more from the middle class than the other catagories of prep. Wear Patagonia, Mountain Hardwear, Northface, and other high quality outdoor gear, drive chevy tahoes with DU stickers. Will NEVER be confused with tree hugging hippies, with whom they share only a love for chacos sandles. Outdoorsy Preps support groups like Ducks Unlimited, not Green Peace. Big into hiking, camping, skiing, hunting, and fishing. Theodore Roosevelt is the god-father of outdoorsy prepdom.
Teenager: Look at that prep coming out of Abercrombie.
Biff: (bitch slapping teenager) Wrong! Look at that prep coming off his fathers yacht, or coming off the TPC golf course, or hunting moose on his family ranch in Idaho.