A rotisserie is a device used to secure meats in place and rotate them over a heat source during cooking. Cooking a rotisserie duck therefore involves placing a whole duck on the spit of the rotisserie in order to cook it over a heat source. Rotating the duck allows all sides of the meat to cook evenly; this is also a good way to drain some of the fat from the bird, since ducks can be fairly fatty and unhealthy. The rotisserie duck generally cooks faster than duck cooked other ways, and it will be a leaner, healthier meal.
The skin of the rotisserie duck is likely to end up crispy from the exposure to the heat source, but the moisture within the bird will generally be retained. Ducks have a fatty layer between the skin and the meat, and cooking a rotisserie duck will help melt off some of this fat during cooking. It is therefore important to place a drain pan beneath the duck as it cooks, as the dripping fat can hit the heat source and cause flare-ups. A well positioned drain pan will prevent the fat from splattering or striking the heat source; it is also possible to place potatoes and vegetables in the drain pan as well to take advantage of the flavorful fat drippings.
Before the rotisserie duck is placed on the spit, it is usually cleaned with water, patted down, and then seasoned. The seasonings used can vary significantly depending on the cook's tastes, though simply adding salt and pepper to the skin before cooking is often enough to add flavor to the bird. A coating of olive oil on the skin will help it brown nicely during the cooking process as well.
Once the rotisserie duck is secured on the spit, it must be placed within a grill or barbecue, or over some sort of heat source such as a campfire. The spit will be oriented horizontally over the heat source. Most rotisseries feature a motor that will automatically turn the spit; this motor may run off of batteries or off of an electrical outlet power source. Sometimes the spit is manually operated, which means someone must tend to the rotisserie during cooking to turn the spit by hand. This is generally an outdated system, as cooking a duck this way can take an hour or more.