There is probably no type of photography that is more disappointing to the beginner than flash photography. Unlike natural-light photography, where what you see can often be what you get, it is difficult to visualize what the effects of using flash will be. Flash is shut off until the moment of exposure, and then its illumination is too brief to visually evaluate what it does to your picture.
The real learning process occurs over time, with trial and error. You should not expect to become an instant expert at flash photography, but persistence and observation (constantly comparing your pictures with earlier ones, and identifying not only the problems to overcome, but the successes you have achieved) will give you the experience you need to control flash and produce consistently-good flash pictures.
Generally, poor lighting conditions results in poor pictures. Usually you do not need flash for normal daytime outdoor shots unless its very gloomy. Keep in mind that flash has a very limited range so it should only be used when the subject is fairly close. Use fill flash to help lighten up a subject which in deep shadow.
It is best to avoid using flash indoors unless absolutely necessary: it tends to burn out subjects and can create harsh shadows. A better choice is to bounce the flash off the ceiling if your camera and flash support this option.
Another option is to let as much daylight in as possible and, turn on all of the lights. You have the option of using fill flash when theres enough light in the scene but your subject is not well lit.
Under certain circumstances you might want to turn the flash off and let the camera deal with the low light condition by increasing exposure. This will not work in very dim conditions, but can give better results than flash. Be sure to guard against camera shake.
Digital cameras are less sensitive to light than traditional film cameras. If you are shooting indoors or in a low-light situation, even with the flash, you should move close enough to the subject for the flash to be effective (no more than 10 feet away). If this is a concern, some digital cameras allow you to use accessory flashes or studio-type lighting.
If you set your digital camera on Auto, the camera will attempt to determine the need for flash based on the lighting conditions, but you still should use the manual setting when appropriate such as using the flash in bright sunlight to reduce intense shadows.
In typical indoor situations there will probably not be enough light to take a normal hand-held well-exposed photo. There are many indoor flash photo opportunities you may be faced with. You may want to cast light on a group of people for a portrait photo. You may want to throw light into a room for an architectural photo. Or you may just want to cast light on certain objects in a lighted room that appears too dark for an exposure.
If your cameras auto-exposure settings say that the photo would require a shutter speed slower than 1/60 of a second then you probably should not hand-hold the camera or the photo would come out blurry. The reason it would come out blurry is because the shutter would be open long enough for any minor hand shake to distort the composition. The use of a tripod or faster film will probably be needed but many of us do not regularly carry a tripod. Most photographers simply use their flash bulb when they are inside.
In order to take effective indoor flash photos there are some techniques you should keep in mind. When using the flash do not point it directly at a mirror or glass that will create a lens flare or just ruin the photo. Stand close enough to your subjects so the flash is actually effective (four to ten feet). Try to make sure your main subjects are about the same distance away from the flash as each other or some that are closer to the flash will appear brighter than ones that are farther away.
Fill flash fills in the areas of a photo that would normally appear too dark. Fill flash can be used for sunny day portraits for shadows on a subjects face or to fill any shaded area that is out of the sunlight. Fill flash can also be used to cast light into a room where there are no windows. Fill in flash is ideal for back-lit and side-lit situations.
In a backlit situation there will be a lot of light in the background but no or little light cast on the front of the subject. This would normally create somewhat of a silhouette effect, but with a fill flash it would balance the photo nicely. But in order for this technique to work, you must be careful to stay in flash range which is usually around four to ten feet. With common cameras in order to add fill flash to a photo just toggle the flash to go off when it normally would not be needed.
Many photographers also choose to bounce the flash off a wall or ceiling to get a softer diffused kind of light commonly sought after for portraits. This kind of flash technique requires a flash that can be aimed in a direction that the camera is not pointed. It takes practice to refine this technique and only a small percentage of photographers actually use it.
Practice using flash in your photos even when it is not necessarily needed and pay attention to your results. The best way to become better at flash photography is to analyze your photos and try to figure out what you could have done differently in order to create a better flash-filled exposure.