Being aware of your body in meditation is vital. It's not something separate from the meditation, and is not an optional extra. It's an integral part of the process of meditating, and it's necessary to spend some time setting up your posture and taking your awareness through your body if you want to meditate well. The more awareness that you can take into your body as you begin your meditation, the better your meditation will go. Otherwise it's a bit like trying to bake a cake without bothering to mix the ingredients first, and without checking to see that the oven is warm enough.
Set up your posture
After you have set up your posture, you feel free to take your awareness through your body.
Body awareness and relaxation
Start by becoming aware of your feet, and with the contact you have with the floor. Really let your awareness fill your feet. The more you become aware of your feet, the more you can allow them to relax. Let the muscles soften and lengthen.
Once you've done that for a minute or two, take your awareness from your feet through the rest of your body, "letting go" as you move through all the different muscles. Become aware of your legs, your thighs, your hips, your back, your shoulders, your arms and hands, your neck, your head and face. When you become aware of a particular area of your body, then soften, relax, let go.
Notice the subtle change in the quality of your experience as you first become aware, and then relax. Often you'll notice more energy, or tingling, or even feelings of pleasure, as your body relaxes.
Pay particular attention to the following parts of your body, where lots of tension is commonly stored:
The back of your neck
Your shoulders
Your hips
Your thighs and calves
Once you've been through your body, become aware of your body as a whole. Then center your awareness on your belly, sensing the calming, rhythmic motion of your belly as you breathe in and out.