Start by bringing your attention to your breathing.
Breathe in through your nose, allowing the air to fill your lower belly.
Then, breathe out through your mouth. Notice the sensations of each inhalation and exhalation.
Continue the breathing exercise for a while. Then, begin to broaden your focus by noticing thoughts, feelings and sensations that arise in the moment.
Notice each thought or sensation as it arises, without judging it good or bad and without pursuing it (letting it become a center focus, in other words).
If you become distracted, return focus to your breathing and then expand your awareness again.