In some situations, traditional matrix metering will give you great results. Matrix metering tends to be the default mode for most cameras. As long as your scene is evenly lit, it will work great. The camera’s light meter will look at the whole picture and determine what the correct exposure should be. The exposure will be incorrect, however, when there are areas of intense white or black in the photo. For example, if you take a picture in front of a window or other bright light source, your picture will end up underexposed. If you take a picture in front of a very dark background, your picture will end up overexposed. By itself, your camera will often judge wrong, and that is why I recommend shooting in manual mode. Matrix metering tends to go hand in hand with shooting in auto or semi-auto. Spot metering tends to go hand in hand with shooting in manual. (I use matrix metering, in manual mode, with auto-ISO turned on for shooting snapshots. I use spot metering, in manual mode, with auto-ISO turned off for shooting portraits.)
Spot metering is when the camera determines the correct exposure by looking at the the area immediately around the focus point. This means that you get to control what you want perfectly exposed. In most cases, it’s the skin of your subject that you want to meter for. To use spot metering, you place your focus point on the face, adjust your shutter speed and aperture to get a correct exposure, then step back and recompose. When you are in manual mode, you don’t have to worry about your camera changing anything when you step back. This method will allow you to correctly expose for your subject. Unless you are changing locations, you do not need to meter again, simply shoot until you have the shot you want. If your background is over or underexposed, it is much easier to repair that in the editing process than it is to repair your subject. It does not matter as much if you lose detail in the background.