There are many methods for bringing the mind to a state of concentration. I'll describe three of the most common methods, beginning with the practice of following the breath.
1. Following the Breath
To begin, you simply sit in a meditation posture and watch your breath. There is not much else to do. Your breathing should be natural, even, and relaxed. There's no need to alter your normal way of breathing. Then draw your attention to your breath, focusing on the coming and going of the breath at the tip of the nose and mouth. There is a sense that you're actually feeling your breath, feeling its movement.
When you do this practice, you're not just watching your breath. As you settle into the practice, you actually become the breath. You feel the breath as you exhale and become one with it. Again, you feel it as you inhale and become one with that breath. You are the breath, and the breath is you. At the end of the exhalation, let your mind and breath dissolve in the space in front of you. Allow a gap; let it go. Drop the experience altogether and simply relax in that space. Then breathe in naturally when your body is ready. There's no rush to take the next breath. Place your mind on the breath as you inhale, feel it, and relax in that space. Read more about this type of meditation . . .
2. Counting the Breath
Whenever your mind becomes fuzzy or forgetful and the sense of nowness is gone, you can bring more precision to your awareness by a simple practice called "counting the breath." To do it, you simply observe your breathing and count each cycle of inhalation and exhalation as one breath. You can start by counting your cycles of breath from one to ten. If you find that your mind has wandered off into a thought at the count of three, for example, then you start over at one. Keep this up until you can count from one to ten without becoming distracted. You can also increase your count to one hundred, if you like. Whatever you decide, there is the same sense of being fully present wherever you are in your count. Counting in this way strengthens your memory and increases the precision of your mindfulness. It naturally counteracts forgetfulness, because mindfulness means "not to forget."
3. Focusing on the Outside World
You can also practice sitting meditation by focusing on a visual object. In this case, everything is the same as in the practice of sitting meditation, except that your attention shifts from a purely internal, bodily experience and connects with an object in the outside world. You can use any object you like: a flower, a pebble, or your remote control. You can also use a picture or statue of the Buddha. Whatever you choose, it's best to focus on just one spot at a time; otherwise, your focus won't be clear. That spot now becomes your primary focus of attention, and your breath becomes secondary. Read more . . .
-- from Rebel Buddha: On the Road to Freedom by Dzogchen Ponlop Rinpoche