A prep doesn't neccesarily come from "old money". Yes, it is true that we have money, but as was mentioned in another definition, we know how and where to spend it. Preps most often spend their lives trying to "get ahead of the pack," and most of the time, whatever we do is for the purpose of outdoing ourselves, and more importantly, outdoing other. Preps spend our lives trying to be the best we can be. (Yes, our entire lives, true preps are part of the preppy lifestyle and culture, and its not just something that is over when you are no longer a teenager)
We don't neccesarily shop exclusively at Lacoste, Polo Ralph Lauren, Saks, etc. We also may shop at American Eagle, Hollister, Nordstrom, Lord and Taylor, or Abercrombie. Or we may mix it up and shop at any combination of the above. One thing, however, is certain: A true prep would not be caught DEAD in clothes that came from Wal Mart or any other similar store.
A prep is extremely invlolved in, and almost obsessed with education. We view education as the basis of our lives. Although we may not attend a true "prep school" in our early years, we almost certainly go on to an Ivy League University, or another university at the same level. Most of us speak at least one other language, most often French and/or German, and we normally study overseas for at least a semester, if not for longer, in order to continue developing the culture with which we were brought up.
Contrary to popular opinion, we do not hate other "groups", such as punks, goths, nerds, losers, etc. They simply do not take the time to associate with us and get to know us, and we don't waste our precious free time, of which we have little due to our academic, extracurricular, and social calendars, trying to make someone befriend us whom we know would only put on a front toward us. I do, for example, have a small number of friends from other groups with whom I associate, simply because instead of talking *about* me behind my back, they talked *to* me and found out that preps really aren't bad people.
In short, preps are those students in your school who use proper grammar, correct peoples grammar without fear of being picked on, speak two or even three languages for fun, not just because of a graduation requirement, apply themselves to school wholeheartedly, yet still fit in a full extracurricular and social schedule, and have to look their best everyday. The people who you swear never sleep! (and lots of times we don't)