Aperture Priority (AV)
'Aperture Priority' is also called 'Aperture Value' depending on your make of camera. But either way it does the same thing and can help you be creative whilst the camera works out tricky stuff like the exposure for you.
The power of this is that you can change apertures to achieve the depth of field you want without having to worry about shutter speeds.
Wide lenses inherently have a very large depth of field and are great for front to back sharpness when used with a small aperture. But a small aperture means less light and even though the camera will find the shutter speed for you - you must keep an eye on what it sets in case it's very slow which will lead to camera shake (a blurred image). If that happens you must either use a tripod or boost your ISO.
Aperture priority or aperture value is probably the mode I use more than anything else. Check out part 2 to see how it can be used with a long lens.
I know this sounds complex but I promise you it isn't. Aperture Priority is one of the simplest things to use that'll have a creative impact on your photos - and make your life easier at the same time.
After completing the 7 Building Blocks of Photography I can honestly say it was worth every penny.