Women's casual resort wear, also called a cruise collection by many high-end designers, is colorful, comfortable and often floral-themed. Look for sundresses in easy-to-wear fabrics like cotton, linen or jersey (jersey is especially good, as it won't wrinkle in your suitcase). White linen or cotton pants also look fantastic at a beach resort--pair them with a pastel cotton T-shirt or tank top during the day and with a dressier silk top for dinner. J. Crew and Lilly Pulitzer have great summer resort-wear pieces.
Tommy Bahama has epitomized men's casual resort wear in recent years with its multitude of tropical-print short-sleeved button-up shirts. You can go that route, or simply pair your cotton or khaki pants (shorts during the day) with a short-sleeved polo-necked top in a light color. Think "country club" and stay away from jeans and T-shirts.
Wear light-colored espadrilles or sandals (wedges are popular during summer) with your casual resort wear. Keep your toes open and only wear flip-flops during the day at the pool or beach.
You can wear flip-flops at the beach or pool during the day, but when you're not in your bathing suit, and during the evening, you should pair your resort wear with a casual loafer-type shoe in a soft leather or canvas. Look for deck shoes or boat shoes.
No women's resort ensemble would be complete without accessories. You can go glamorous in a wide-brimmed straw hat and dark sunglasses. Chunky jewelry like an enamel bangle or a beaded necklace will complete the tropical-vacation look. And don't forget a roomy straw tote bag to haul your belongings around during the day (in the evenings, stick to a small clutch in a bright color).