There are 16 varieites of sweet potatoes. Go for jewel or garnet sweet potatoes, which are the ones with the deep orange flesh. They tend to be moist and more tender, perfect for roasting or in casserole. Look for small to medium size sweet potatoes, the larger they are the starchier they become. And make sure the skin is tight, unwrinkled, and there are no signs of bruising.   Store raw sweet potatoes in a cooler, dry and dark location with good ventilation.