* Put the skillet over moderate heat for a few minutes. Then add the oil or butter and swirl it around until the palm of your hand feels hot when you hold it close above the pan. If you are using oil, it should also shimmer slightly.
* Don't crowd the pan as you add the ingredients. If the pan is too full, the temperature will drop and the food will not brown properly. Instead, the juices will leach out and the food will poach in its own liquid and ultimately overcook. If you have a lot to sauté, cook in batches.
* Conversely, if the skillet gets too hot and the food starts to brown too quickly, pull it off the heat briefly to cool it down.