At any moment, you must divide your mental effort amohng tasks, each of which requires more or less attention. However, as skill becomes more automatic, it requries less attention. Very intense stimuli usually command attention. Big, bright cars probably get more tickets than small, dull ones. Loud, irritating comedian Don Rickles ahs made a career out of the first principle of attention.
Repetitious stimuli are also attention-getting.
A dripping faucet at night makes little noise by normal standards, but because of repetition, it may become as attention-getting as a single snd many times louder. This effect is used repeatedly, so to speak, in television and radio commercials. Attention is also frequently related to contrast or change in stimulation. The contrasting type styles draw attention because they are unexpected. Change, contrast, and incongruity are perhaps the most basic sources of attention.