While my camera club is having its annual break, I did a lot of event shooting. I shot at parties and outings, posting the images in Facebook. I think the exercise has proved to be invaluable to me. I learned a lot about exposure control (and still haven't mastered it yet!). I am even convinced that beginning photography can be learned from the approach of mastering exposure. Most photography courses start by introducing the newbie to the concept of depth-of-field, motion blur and other creative shootings. If anyone is keen to take up photography seriously, he should start by learning to expose correctly.
First, it is necessary to start by shooting in manual mode. Learn to use the exposure control to bias the exposure one way or the other as necessary. Once you have mastered that, then you can start using the A mode or S mode when you like (note: not before mastering the M mode).
Second, learn to handle ambient light. There's front lighting, overcast front lighting, back lighting, and side lighting. Learn when and how to shoot for best result. Next, learn to handle special lighting conditions such as dawn/dusk, snow, sea, fireworks, and night photography.
Third, learn to use flash, first as fill-in flash, then as main light source. Learn to use built-in flash, as well as off-camera flash for better result. Using flash as main light source in different artificial lights takes time and practice to master. When using flash as the main light source, it is necessary to master the concepts of sync speed and guide number.
Fourth, learn to use accessories like the light meter, gray card, polarizer, and ND filter. All these are essential tools to gain complete control over every situation that challenges your exposure control to the limit.
Indeed, exposure is the most important aspect of photography; even more so than composition or creative shooting. One cannot have a well composed picture with bad exposure. Likewise, a creative shot will fail to impress, if incorrectly exposed.