Q: Am I supposed to think the mantra in particular locations in the body? Sometimes it gravitates to physical locations in me.
A: No, we do not deliberately physically locate the mantra. This is a delicate question because the mantra has a vibratory quality that awakens the nervous system in particular ways, as previously discussed on the question about the vibratory quality of the mantra. So it might be experienced in some place or another, as you said. But we do not favor that. We continue with the simple procedure for using the mantra, always.
The nervous system in its most subtle realms is like a tuning fork -- rather, like a multitude of tuning forks, with just a few tuning forks harmonizing the vibrations of all the others. The mantra resonates with these few leading tuning forks. Later on, we will enhance the mantra to broaden the influence of this tuning fork effect. The result will be broader and deeper immovable inner silence, also experienced as pure bliss consciousness coming up in us.
If you find the mantra occurring in particular locations, that is okay. We don't resist that. Nor do we encourage it. Just as we let the mantra settle down naturally to quieter and quieter levels, so too do we let it occur in the body wherever it is naturally. If it doesn't occur in any particular place, that is okay too. It is not about physical locations. The mantra naturally resonates according to the complex purification process going on inside us while we are meditating. All we have to do is follow the simple procedure of thinking the mantra easily, and picking it back up easily when we realize we have been off it.
Another reason this question you ask about location of the mantra is a delicate one is because soon we will be discussing pranayama, and taking up an advanced breathing practice before each meditation session. This will involve moving the attention in a particular way through the physical body in concert with the breath. We will be using two practices in succession – pranayama and meditation, each quite different in its procedure. They will complement each other tremendously, as you will see. This will be the beginning of the all-important integration of advanced yoga practices. Each part will be done independently. Yet, with these two methods taken in succession, an integration will begin to occur in us. The whole will be greater than the sum of the parts. Instead of using one natural pathway to the divine in us (the mind), we will be using two (adding the breath). Together, these will transform the nervous system at a more rapid rate, and the greater purification and corresponding experiences will reflect this. This process of integration of practices will be gradually expanded to more fully embrace all of the natural pathways leading in through us, and coax pure bliss consciousness out through us in increasingly dynamic ways. This integration of practices is a delicate process, much like playing a musical instrument. We must be able to do one thing at one time and do another different thing at another time. With some practices, we will be doing several different things at the same time. It is all part of a natural unfoldment in us, and the practices themselves will become natural in due course, and automatic. The results experientially cannot be done justice with the written word, except perhaps in poetry. You have to go there and see what it is for yourself. It is the real "final frontier." It is the glorious cosmos, and you are the doorway.
The guru is in you.
Note: For detailed instructions on deep meditation, see the AYP Deep Meditation book.