Advice on this has varied over the years, including the advice Frank gives. The latest research shows that from a health point of view, washing is not necessary. Any microbes that you'd wash off will be entirely destroyed by heat when you cook the meat. It's actually far more important to wash your hands, your cutting board, and your utensils since they won't be sterilized by cooking. How do I get the best flavor?
That depends on whether you're after a mild and delicate flavor, or a strong and robust flavor. The younger the bird, the milder the flavor. A game hen, which is five weeks old, will have the mildest flavor of all. A broiler, at seven weeks, will still have a quite mild and delicate flavor; a roaster, on the other hand, is usually about five weeks older than a broiler and it will have a much more pronounced "chickeny" flavor. (Frank and I enjoy chicken at all ages, but if we had to choose on flavor alone, we'd most often go for the roasters.) For a really strong, chickeny flavor, see if you can find fowl or spent hens or stewing hens. These birds are around 18 months old, which means they're going to be quite tough, but if you use them in soups or stews, they'll add an excellent flavor.
From the Perdue Chicken Cookbook