Be prepared to fry the potatoes twice: once to cook them so they fluff inside and again to get them crispy on the outside. When I use an electric fryer, I always follow the manufacturer's instructions. To make good fries in a pot on the stove, a deep-fat thermometer is essential. It ensures that the oil is at the proper temperature for deep-frying and lets you check that the oil isn't overheating, a potentially dangerous situation. A mandoline is a very useful slicing tool for cutting the potatoes (and other vegetables) quickly and to a uniform size. Both the deep-fat thermometer (also called a candy thermometer) and the mandoline are available at most cookware stores. The third essential is a pot that is large and tall enough to contain the oil without overflowing when the potatoes are slipped in.