In Season: Though sweet potatoes are available year-round, they're at their sweetest in fall and winter. They are sometimes mislabeled as yams, which are actually not widely available in North America.What to Look For: There are two main varieties: The orange-fleshed sweet potato has sweet, bright-orange flesh that takes on a creamy texture when cooked. The yellow-fleshed variety is more mealy and less sweet than orange sweet potatoes. Choose sweet potatoes that are very firm, with no areas of softening, sprouting, or wrinkling -- all signs of age. Sweet potatoes vary quite a bit in size and shape. Those that are straighter and uniform in size are easiest to peel and cut.How to Store: Keep sweet potatoes loose in a cool, dark place for up to one month. They should never be kept in the refrigerator, as their natural sugars will convert to starch, making them less sweet.