Thanks for overnight stays at five-star hotels with 1,000 thread- count sheets, gourmet room service and othet luxurious amenities, seasoned jet-setters look stunning for their busy agendas. For an extra little boost, experts at La Prairie at The Ritz-Carlton Spa (50 Central Park So., 5216135) buff bodies with an indulgent cream of diamonds, freshwater pearls and quartz crystals before applying the signature kin caviar lotion in the Diamond Perfection treatment. The result is exfoliated skin that is toned and moisturized. To enhance smile power, dentist-to-the-stars Dr. Jan Linhart (230 Park Ave., Ste. 1164, 682-5180) uses the PEARLINBRITE™ laser rooth-whitening system to brighten teeth up to 10 shades in less than two hours.