Meditation is a purposeful focusing of the mind. Athletes and martial artists practice meditation to enhance their performance. Yogis, Buddhist monks and spiritual seekers practice it to attain spiritual insight. Ordinary people around the world practice it to regulate their fight-or-flight system, decrease stress, regulate emotions, and improve interpersonal relationships. Though many meditation postures are available to your teen, if she is a beginner, all she needs to do is follow a few basic guidelines: (1) Make sure her breathing is not constricted in any way; (2) Find a posture that won't make it too easy for her to fall asleep; (3) Meet her meditation experience with relaxed dignity.
Mindfulness meditation is a process of getting to know your inner landscape. It can take several forms. Jack Kornfield, in his video, "The Inner Art of Meditation," recommends this way for beginners: Your teen should relax and watch his breath. Eventually his mind will start to wander. As it does, he shouldn't try to stop it, but instead just watch calmly. Encourage him to label the emotions and thoughts as they pass through: impatience, planning, contentment, remembering, or whatever else passes through. Your teen shouldn't engage the things going on in his mind; he should just watch and label. Doing so gives him a new perspective on his day-to-day thoughts, enabling him to get caught up in them if he chose to do so.
Mantra meditation focuses on a word or phrase. The mind is a little like a hyperactive monkey running loose in your living room. It bounces from distraction to distraction, running over everything that gets in its way. Focusing on a mantra is like giving the monkey a toy to occupy it for a while. If the mind is focusing on something, it's less likely to try to focus on everything.
Project Meditation says that your teen's mantra doesn't have to be the classic "Ommm." It can be a word or phrase that means something to your teen, perhaps something from your family's religious background, or a suggestion like "relax" or "courage." Your teen should clear her mind, relax and breathe. In time with her breath, perhaps on the exhale, she should repeat her mantra, either aloud or in her mind. Doing so helps bring the mind to focus.
The heart breath is a form of meditation with verifiable physical benefits. To do the heart breath, your teen needs to relax and breathe on a ten-second cycle--five seconds in, five seconds out. As he does this, he needs to breathe a positive mental state into the region of his heart. That state might be calm, appreciation, gratitude, or compassion. Tell him to feel that state filling his chest as he breathes.
What happens to your teen's body when he does the heart breath is profound. His heart rate shifts to become more "coherent." In other words, if you were to plot his heart rate variability on a graph, you'd see a smooth, regular, sine-wave like pattern. This change in your teen's heart rhythm then influences other rhythms in his body, including blood pressure and brain waves. All the systems of his body begin to work together more closely, making him more creative and intuitive.
If you want more information about the heart breath and its effects, investigate HeartMath.
Compassion meditation builds one of the traits most central to humanness: the ability to empathize. Your teen should begin this like any other meditation by relaxing and becoming aware of her breath. Then she should let her mind drift toward someone she loves, it could be either a person or animal. It could be someone who is ill or struggling, someone she knows in the military, someone she is estranged from or someone she wants a deeper connection with. Gradually, your teen needs to let herself drift inside this person's perspective. What would it be like going to work, being with family, dealing with the things this person is dealing with. Tell her to see the world through this new set of eyes, feel with a new heart and stay there for a while before coming back to her own perspective. As your teen does this, she should feel free to say a prayer for this person or express a wish for their well-being. As she finishes this meditation, she will need to return to her breath to quiet her mind and emotions and center herself again in her own perspective.