When fries aren't the same size, some will burn, and others will be hardly cooked. Fight this by cutting them into thin strips of about one centimeter in width. If you prefer thicker fries or wedges, cut accordingly, but there is a risk of ending up with soggy fries.
Starch keeps the moisture in the fries from escaping during the cooking process. Thus, soaking out the starch from the fries will help them be drier and crunchier while cooking. Soak in a large bowl of water for one or two hours before cooking.