This is an extremely simple way to prepare couscous so that it is moist, tender, slightly chewy, and in individual grains rather than clumps. It is from the cookbook, "Arabesque: A Taste of Morocco, Turkey, and Lebanon", by Claudia Roden.
Mix warm water with salt. Place couscous into an oven-safe dish. Gradually add salted water, stirring vigorously so that it is absorbed evenly. Leave to swell for about 10 minutes, then mix in oil and rub the couscous between your hands above the bowl to air it and break up any lumps. That is the important part.
Put the dish in an oven preheated to 400F and heat through for 20 minutes, or until it is steaming hot. Before serving, work in butter and fluff it up again, breaking up any lumps.