The main difference in the skin from various types of poultry is the thickness of the fat layer that lies just under its surface. For example, on ducks it is much thicker than the relatively thin layer on chickens. As a result, it is relatively more difficult to prepare duck skin in such a way that it is crisp, while still ensuring that the duck meat is cooked to tender and juicy perfection.
If the skin is thick, it can be difficult to extract sufficient water without overcooking the underlying meat. To help the process along, the skin can be dried out somewhat by placing it under a fan or in a freezer. Freezing is the usual way of proceeding in the case of Peking duck, which is renowned for its exceptionally crisp skin. Another possibility is to loosen the skin from the meat so that the heat has a harder time penetrating into the meat.