The more liquid you are using, the higher the sides of your pan should be. This may seem pretty straightforward, but deciding when to use a skillet (i.e. fry pan) or a sauté pan can be something of a toss up. The skillet's light weight and sloping sides are designed for easy maneuvering over high heat. Flipping, shaking, and swirling isn't just for style, either: doing so keeps everything cooking evenly. A sauté pan's high walls reduce splatter and mess, so these are best for cooking in sauce or lots of oil.
Above: If you want to learn how to toss food in a skillet, check out the tutorial on Serious Eats. Then try out your new skills with 39 Delicious Things You Can Make In A Skillet.