Photography Tips : Be as prepared as a boy scout and always be ready to snap a shot. Most digital SLRs have nearly instantaneous startup times, and it takes almost no extra battery power to leave your camera on.
Keep your camera on one of the semi-auto or full automatic modes for unexpected pictures before your subject flies, drives, or runs away. You can always switch back to your preferred mode when you have time to adjust for a stationary subject. Sometimes you only have a split second to capture a great shot.