Photography is all about light. Photographs are recorded light. How we control the available light and add additional light when needed is the basis for all photography. There are many different controls and methods for controlling light available to today's the photographer.
Understanding Your Camera's Light Meter
This device takes into account all of the settings on your camera (aperture, shutter speed, ISO, etc) and tells you what type of exposure that combination plus the available light will create on the cameras sensor. The first step to understanding photography lighting is to understand this tool for measuring light.
What is a Light Meter?
A light meter showing proper exposure
A light meter is an instrument inside your camera that tells you if the amount of light reaching the cameras sensor or film will be enough or too much to properly expose your image. The light meter takes into account your shutter speed, film speed, and aperture settings.
Your camera's light meter shows you the amount of light in aperture settings. Each dot on the meter represents a partial "stop", or aperture increment. The numbers represent whole stops. Even though your F-Stop setting controls the aperture itself, the meter readings will also change if you change your ISO setting/film speed or shutter speed.
A light meter showing one stop overexposure
Even though most of the time you will want to keep your meter reading in the center, there are times you will need to deliberately overexpose or underexpose your images slightly. Sometimes this is for artistic effect but usually it is because you are shooting in conditions that can confused the meter.
Examples of times to overexpose
Subject is very dark in comparison to background
Snow
On a bright day if your subject is in shadow
Examples of times to underexpose
Subject is very light in comparison to background
To achieve a silhouette effect
On a overcast day to increase color saturation
Automatic Exposure Bracketing (AEB)
Im sure at times your trying to photograph a subject with tricky lighting or lots of variation between bright and darker areas but were not sure what exposure setting to go with?
One way to work in such situations is to manually play around with your exposure control and take a series of shots – the problem with this is that it takes time and if you are photographing a changing environment (for example a sunset which changes from moment to moment) you can lose ‘the moment’ while you get things right.
Most DSLRs (and some more advanced compact cameras) come with a feature called ‘Automatic Exposure Bracketing‘ (AEB) which can be useful to learn how to use in such situations.
By selecting it you can quickly take three shots (usually three) at different exposures without having to manually change any settings between frames. You can see an example of this below
When you select Automatic Exposure Bracketing the camera will choose one exposure (based upon what its metering thinks is right) and then it will take one other shot on either side of this best guess (one over exposed (as in the left shot above) and one underexposed (as in the right shot above)).
This way you end up with the three images in a series with exactly the same composition but at different exposures for you to select the best of later on.
If you have the camera in burst mode (continuous shooting) the three shots will be taken if you hold down the shutter for a burst of three shots. If you’re in single shot mode the shots will take as you depress the shutter three times. 
Check out your manual to see how AEB works on your digital camera. Most will allow you to change the variation between shots by different ’stops’. For example you might want a big variation between your three shots and would select a ‘2 stop’ gap or you might only want a slight variation and choose a ‘half stop’ gap. I generally start with a ‘1 stop’ variation and work from there. 
PS: to give you a little more control in Automatic Exposure Bracketing mode you can use it ether in Aperture Priority Mode or Shutter Priority Mode. Using AEB in Aperture Priority mode will all you to choose the aperture you want for the shot and telling the camera to make the variations in shots by varying shutter speed. Alternatively using AEB in shutter priority mode will keep the shutter speed at the speed you select and tell the camera to vary the exposure by changing the aperture in your shots. This method can also be used to produce HDR (high dynamic range) image which is kind of layering the three different exposures together to form one image like my example. I use Dynamic photo HDR 4 along
With the use of auto bracketing and some quick changes to the saturation and contrast on photoshop or lightroom you can really give your images that professional look.
