Select lettuce heads that tend to feel heavy for their size. This means they have retained their moisture. Romaine should also have firm, crisp leaves and avoid any lettuce that has dry, withered leaves on the outside. Check the leaf color. The more colorful the lettuce is, the more nutrients and healthful antioxidants the lettuce contains. The color should be bright and intense. Avoid lettuce with brown or yellowed leaves. The flavor of Romaine is slightly bitter although it is an exceptionally crisp lettuce. Romaine has long, narrow leaves with thick ribs. The most flavorful part is toward the center of the head -- this is why you will often see bags of Romaine hearts, packaged with the outer leaves removed. It's most well known in Caesar salad.