No matter how good you are with your camera, you will forget to check the settings on your camera. The recent not guilty verdict set off a night of protests in Los Angeles. Here a protester tells me, "you aint takin no pictures". This was just the first of many threats and being bumped around for me. I am pretty good at knowing what the settings on my camera are. It isn't often that I will grab my camera and forget to check it to make sure I didn't bump my settings. Tonight, I was driving away from the protest area, and drove upon a fast changing situation at the corner of Adams and Crenshaw in LA. I reached over to grab my camera and started shooting a mob of violent protesters jumping on cars and police screaming into the intersection.
After it was over, I was horrified. I had shot the entire event with the wrong settings. I didn't notice it in the viewfinder.
A good way to make sure this doesn't happen to you is for you to use your preset functions. Most DSRL cameras will have three of these spots. You can set each one to a setting you use frequently, and then in a hurry you just turn the dial to a preset position. Each function will be set with a different shutter speed, aperture, ISO and some other settings. Don't wait to set these functions, because sooner or later you will bump your camera settings without knowing it.