Cut all edges of potatoes to make a rectangle. Slice into 1/2″ slabs. Cut each slab into several sticks.
Immerse in cold water for at least 30 minutes (you can also store them in the fridge overnight this way). Alternatively, rinse potatoes under cold water until water runs clear. You are trying to get rid of all the loose starch that will make the fries stick to each other.
Carefully dry off potatoes with towels right before frying.
Preheat oil to 320F. Cook fries in small batches (about a handful at a time) for about 5 minutes, or until cooked through but not brown. Be sure to let oil heat up between batches. Drain over a cookie sheet. Let fries sit for about 30 minutes.
Heat oil to 375F. Cook fries until light brown and crispy, about 2-4 minutes. Drain over a cookie sheet.