A scene will draw your attention for any number of reasons. Action or movement of some sort, an interesting or pretty face, a dramatic shape, something that doesn't belong. However, the thing that's sure to catch your eye will be an out of place patch of color.
The bright hues of a row stools in a drab lane or a riot of orange in a busy city street draw the eye like magnets. It's not enough just to capture the color though. A puzzled expression begs the question of what is puzzling the subject. Perhaps he's just been told he has to bring in all the oranges at the end of the day. A faded reminder of years past makes you wonder what the penalty was for parking beyond the line. A blank doorway adds mystery and balance to a composition. Look for the color, but try to weave bit of a story around it as well.
You can cheat a little and use the old trick of desaturating all except the object of interest, but it's an effect that is often used without much thought and can lose its impact if you do it too often. I believe an image will have more impact an object can stand out in its environment without resorting too much manipulation.