One of the biggest ways that you can add punch to your photos, is through the use of off camera flash. By taking a flash unit (or any light source really) and moving it away from the camera, you can totally change the mood of the photograph. In the photo below, if we were simply using natural light with no flash, we would have had to choose between having a photograph of the sunset with the subject completely dark, or a photo of the subject with the sky and sun completely overexposed.
To solve this, we first place our camera in Manual mode (M) and get an exposure for the bright region of the sky. Simply make your adjustments and find where your in-camera light meter gives you a good exposure reading. We then want to drop this exposure by a half or one full stop to darken it slightly. If we take a picture at this point, we will have a beautiful photo of the sunset, however as the subject is not as bright, they will be completely dark and possibly simply a silhouette.
We now add in some light to bring up the lighting on our subject. This lighting can be a constant on light (such as a lamp, work light, even the flashlight on your cell phone will work) or a strobe flash such as what we use. Placing an opaque white fabric in front of the light will soften it and create a much softer light for your portrait. In our case, we use a softboxes and shoot-thru umbrellas, depending on the situation. Placing the light about 45 degrees to the subject and just above eye level generally produces a beautiful effect.
You can use this exact same set-up when you want to create dramatic portraits in the middle of the day. The key to this is experimenting with different lights, settings, and light placements. You will see that many of our photos use lights to create a more dramatic photo, sometimes slightly off center ranging all the way to a 90 degree side light. In some cases, even placing a light behind the subject and pointing it toward the camera to get the look that we want.