You might think mindfulness and meditation are only for adults, but kids and teens can also experience great benefits from these practices. All you need to teach these skills are an appropriate approach and a patient attitude. Parents should practice these exercises with their kids. This helps them see that even adults need to work on calming down, and reinforces that this is a life-long practice. Practicing together also builds a deep connection between you and your child.
Most of these exercises are done sitting and preferably with the eyes closed (except for the raisin and walking meditations). In each of these exercises, start by preparing your child to relax. Depending on your child's age and ability, a few gentle stretches can make the body feel more comfortable. Make sure where you are meditating is free from distractions and feels cozy. If it's appropriate, dim the lights. Ask your child to come into a comfortable position sitting, standing or lying down, depending on which meditation you are practicing. Almost all of these practices are appropriate for both kids and teens.
As with all mindfulness exercises, it is best not to practice with expectations for how (or how long) your child will meditate. Let them develop their practice gradually - start with a few seconds for young or restless kids, and encourage them by praising what they've accomplished. Eventually, they will come to enjoy the peaceful feeling and will meditate longer, naturally. At that point, you might encourage your child to describe how they feel after meditating.
If your child gets frustrated, let them know it is normal for thoughts to wander away from where we want them. You might even throw in a personal example. That's what meditation is all about. It's why we practice! To learn to bring our thoughts back under control.
Exercises adapted from Yoga for the Special Child and Yoga for Teens.
Just some thoughts about yoga as I go...