So, now you've begun to learn how to relax your body and focus your mind. You have been doing something else though. With the practice you've been doing, you've actually been training your body and mind. You have been training them to react to your breathing. You will find that you can actually just take a couple deep breaths through your diaphragm and you will feel calmer and more relaxed just from that. Not necessarily the same as a complete session, but good for a quick fix when you need it.
But now, we will be continuing the training of the relaxation of your body. Having now achieved some relaxation through breathing, we will now work on muscular relaxation. This relaxation will help calm your muscles and help reduce or eliminate any physical difficulties (random feelings and such) that might pull your attention from your meditation.
This reduction in physical feelings will result (at least this is how I feel) of floating, providing an excellent jumping off point for both meditation as well as astral projection. This lack of physical sensation allows one to concentrate completely on the visualization of the meditation as well as just being an excellent form of relaxation when you have the time.
For this exercise, I recommed you actually lay down. Begin with the breathing exercise from the first lesson. Once you have achieved a regular rhythm and feel comfortable begin the relaxation. Concentrate on your toes, visualize the tension and stress within them draining down into the ground and replace this with neutral relaxing energy. Once your toes are relaxed, move the relaxation to the rest of your foot. Do the same thing there as you did to your toes, drain the stress and replace with relaxation. Continue in sections up your leg: your ankles, lower legs, knees, upper legs, your waist and then abdominals.
Once there, switch over to your arms, start with your fingers, palm, wrist, lower arm and upper arm. Go back down to your abdominals and relax the muscles up your torso and especially the many small muscles surrounding your spine. Work up to your shoulders, your neck, then jaw, your face (yes your face, you'll be surpised at the feeling), and finally your scalp.
If at any point you feel you need to move back to some part of your body that you've already been over, go back and do the relaxation again over that area before continuing on. During the relaxation, make sure you keep breathing down through your diaphragm. Once your body is complety relaxed, just lay back and enjoy the feeling.
Just as a personal note, this is a really good exercise to do right before going to sleep. I tend to sleep and wake up better after doing this, but that might just be me. =^,^=