As a photographer who is dedicated to your craft, one way you can distinguish yourself from a casual hobbyist is through your mastery of lighting. A new video by Mark Bone gives 5 guidelines you can consider when you want to add light to a portrait. Although Bone is a filmmaker rather than a photographer, these tips apply to photography as much as they apply to filmmaking.
Mark discusses using both natural light and artificial light. One of the more interesting ways he uses natural light is in combination with an app called Shadowmap that shows where shadows will fall in a particular location at any time of day that you chose. Using the free version, you can search the app for any location in the world and you will see a graphic that shows all of the buildings and natural structures in that area and where the shadows that are cast by these objects are falling at that time. You can use a slider to quickly change the time of day and the graphic will show how the shadows move as time passes. This is useful whether you are looking for open shade or sunlight in which to shoot.
Check out the video for a demonstration of the app as well as details on the aforementioned lighting tips.