Chicken is a great first cook for a WSM. Most people usually run chicken at higher temp and if you leave the water pan out the drippings will sizzle on the coals and give a wonderful aroma to the whole process. It also helps build up that magic layer that takes the "new-ness" away on the inside of the main body also.
If you have never tried it Cornell Chicken is a great recipe and pretty straight forward. Just baste the chicken every so often as it cooks. It's also called "Fireman's chicken" or "Roadside chicken" and there are several threads about it with a couple of recipe variations on this site.