In order to create good conditions for being aware, you need to have an open chest, with a sense of spaciousness across the front of your chest between your shoulders. You can encourage this sense of spaciousness by taking a few deep breaths and filling your upper chest. As you breathe in, the front of your body with rise (see the arrow on the photograph). Feel the openness across the front of your upper chest and, at the same time, relax your shoulders, letting them fall and roll back (like the arrow behind this meditator).
If, while sitting, you feel any stretching in your shoulders, it probably means that you need to have you hands supported higher.
Your arms weigh a lot. If your hands are not supported, then your shoulders have to carry all of that weight. That means either that your shoulders will tense to bear the weight of your arms, or your shoulder muscles will be overstretched. Either way it's going to be uncomfortable.
Make sure your hands are supported. If you're in a low cross-legged position, then you may be able to rest your hands comfortably in your lap. However, you may want to have your hands supported higher. This will allow your shoulders to roll back further and be more relaxed. If you're sitting in a chair, you can usually rest your hands on your thighs, but some people with long backs may need something to support the hands. If you're kneeling, using cushions or a stool, then you may need to have some substantial support for your hands. In this case another meditation cushion, or perhaps a sweater or blanket tied round the waist, can be used.
The position of your head is very important. Your head should be balanced, and should almost seem to float effortlessly on top of your spine. You can imagine the crown of your head being drawn upwards, as if the string of a baloon were attached to it. Your chin should be slightly tucked in, and the back of your neck should be long and relaxed. So as you tuck in your chin, feel the muscles on the back of your neck relaxing and lengthening.
If your chin is tucked in too far, so that your head hangs forward, then you'll find either that you tend to feel dull and sleepy, or that you become caught up in circular, and often not very positive, loops of emotions.
If your head is tilted too far back, so that your chin is in the air, you'll find that you tend to get very caught up in thinking, and that you become rather "speedy."
But when your chin is nicely tucked in, you're able to be aware of both your thoughts and emotions without getting lost in them.
