The first thing you need to do, if you don't have them already, is buy some white plates -- bigger is better, and a wide rim is ideal. You might think a fancy patterned plate would look, well, fancier, but you want the focus on the food. A white plate really makes your food pop -- it's a blank canvas, just waiting for your mouthwatering work of culinary art (or at least it will look like a work of culinary art). Restaurants that serve, say, Caribbean food can get away with brightly colored plates, but for everyday purposes you can't go wrong with white.
Getting the plates is easy -- now you have to make the food look good.