Lots of water in a big pot, a little salt, stir it frequently while cooking and don't overcook. When done drain into a colander and rinse it with steaming hot water (removes any starch residue and makes it more pliable). Karen's advice is great: when you spaghetti has drained put it back in the pot, add a little butter (I usually add grated Parmesan cheese as well for flavour) and voila! it's done!!