Introduction: The Three Kings of Photography: ISO, Shutter Speed, and Aperture.
In order to take more awesome pictures, one must have a fairly good understanding of ISO, Shutter Speed, and Aperture, sometimes called the "exposure triangle". A brief introduction to the trio would be thus: ISO is the level of sensitivity of your camera to available light. The lower the ISO number, the less sensitive it is to the light, and vice versa. The only problem with a higher sensitivity is that it makes your pictures grainy. The aperture is a hole inside the lens that lets light in that can vary in diameter. It also brings more or less objects into focus depending on the size. Shutter speed is how long the shutter stays open and takes in light, making the picture brighter or darker.
Step 1: ISO: Light Sensitivity
When taking pictures in high light levels, it is best to stick with your camera's base (lowest) ISO setting. If the light levels are low, then it is easiest to set the ISO to AUTO and go from there. But, as you can see from the pictures, a high ISO makes the pictures grainy.
Step 2: Aperture: Focus
When trying to blur the background of your image, the way to do it is by putting the aperture to its lowest setting, or just a lower setting. Another purpose of it (as you can see in the pics) is singling out one (or a few) in a line. Making some in focus and the rest out of focus. The larger the number setting, the smaller the aperture is, so if you want more in focus, you will have to change the ISO and/or shutter speed to accommodate.
Step 3: Shutter Speed: Frozen or Moving?
If you want to freeze motion, dial up your shutter speed. If you want a little motion blur, slow it down. The only drawback is that a faster shutter speed will make a picture darker. If you want do do something like light-painting, set the shutter speed to RREEAALLLYY SSLLLOOOWWW. In the end, one of the many secrets to a picture is the perfect compromise of ISO, shutter speed, and aperture.