For guys, concentrations in Vineyard Vines with Nantucket reds purchased years ago at Murray's Toggery Shop are de rigeur, coupled with ribbon belts, Sperrys, and various subtle J. Crew accoutrement, the occasional old Ralph Lauren polo thrown in for good measure. Ladies, however, take more varied prep courses, focusing on nuance. They'll often major in dresses purchased at J. McLaughlin on Charles Street, or Sail to Sable (started in CT by a Trinity grad, no less), paired with Stubbs & Wooten skull and crossbone slippers (for fun!), or Dubarry boots, bags from Annabel Ingall, MZ Wallace, or Gigi on their shoulders.
And since it's easy to fall behind if you're not paying close attention, don't fret: summer style courses are offered in Chatham, Harwichport, Montauk, and, naturally, Nantucket.