From The State of Mind Called Beautiful (Sayadaw Pandita, 2006):
Only when one notes and observes the presently arising object will one see its true nature. There is no axiom more basic. Wisdom means clear-cut, distinct, discerning, direct knowledge. Dharma, the true nature of reality, can only be seen at this very moment—in the moment of actually seeing, hearing, touching, tasting, smelling, or thinking. When the abdomen is rising and falling due to the breathing process...when eating, when opening the eyes, this is when the true nature of the object can be captured by the attentive awareness.
In life, we are all too often caught up in thinking and worrying and planning and reminiscing. Why? How does that serve us? "I have to plan, so that I know how to best utilize my time, or know how to properly do something," you might answer. This is true. But are you planning when you choose to plan, or does your mind go on planning and testing and thinking when that is not your intention? There is a time for planning for the future and reminiscing about the past, but we often find our minds doing these things when that was not our intention, or doing them to excess. The antidote to this waste of mental cycles is mindfulness: noting and observing the most obvious presently arising object, be that your breath, a thought, an emotion, a sensation (painful/pleasant/neutral), etc. When you see it occur, name it with a simple name. (For the abdomen in breathing, "Rising...Falling," for a movie that starts to play in your head, "Seeing...Seeing")
1-Minute Practice: Watch and name the rising and falling of your abdomen as you breathe. If a thought intrudes, label it "Thinking." Don't follow the train of thought, just note it. If it dissipates, return to "Rising, Falling." If another thought arises, "Thinking."