Sitting is the most commonly recommended posture. There are a number of classic seated poses, but Sukhasana (Easy Cross-Legged Pose) is obviously the most basic. More flexible meditators prefer Padmasana (Lotus Pose).
Sitting in a chair also works and is often the best choice for beginners. Be sure that your spine remains upright and that you feel steady and comfortable. To maximize comfort on the floor, place a cushion or folded blanket under your buttocks to elevate them and gently guide your knees down toward the floor. This helps support the natural lumbar curve of the lower back. Some people prefer kneeling “Japanese-style.” You can buy small, slanted wooden benches for this position.
Relax your arms and place your hands on your thighs or in your lap, with the palms in a relaxed position facing up or down. Roll your shoulders back and down and gently lift the chest. Keep your neck long and the chin tilted slightly downward. Depending upon which technique you are following, the eyes may be opened or closed. Breathing is natural and free.
A moving meditation—highly recommended by many teachers—may be an enjoyable option for you. The challenge of this form is to walk slowly and consciously, each step becoming your focal point. Destination, distance, and pace are all incidental. Relax your arms at your sides and move freely, coordinating your breath with your steps. For instance, you might breathe in for 3 steps and breathe out for 3 steps. If that feels awkward or difficult, just breathe freely. Although you can practice walking meditation anywhere, choose a setting you particularly love—the ocean, a favorite park, or a meadow. Remember, getting somewhere is not the issue. Rather, the complete involvement in the act of walking becomes your meditation.
Standing is another meditation practice that can be very powerful. It is often recommended for those practitioners who find that it builds physical, mental, and spiritual strength. Stand with your feet hip- to shoulder-distance apart. Knees are soft; arms rest comfortably at your sides. Check to see that the whole body is aligned in good posture: shoulders rolled back and down, chest open, neck long, head floating on top, and chin parallel to the floor. Either keep your eyes opened or softly close them.
Even though lying down is associated with relaxation, the classic Corpse Pose, Savasana, is also used for meditation. Lie down on your back with your arms at your sides, palms facing upward. Touch your heels together and allow the feet to fall away from one another, completely relaxed. Although your eyes may be opened or closed, some people find it easier to stay awake with their eyes open. A supine meditation, although more physically restful than other positions, entails a greater degree of alertness to remain awake and focused. Therefore, beginners may find it more difficult to meditate in this position without falling asleep.
Source: Mara Carrico, Yoga Journal, "A Beginner's Guide to Meditation", http://www.yogajournal.com/article/practice-section/let-s-meditate/