On the physical level, after letting go of tension in your shoulders, arms and hands, you just have to sit or lie down, comfortably support your elbows, rub your hands together and cover your closed eyes with the cupped palms of your hands. Since the eyes are designed to receive and focus light, when the light is reduced or eliminated and the eyes don't have to focus on anything, there is nothing for them to do but relax. There is nothing for the body to do but breathe and allow itself to be supported.
Some people find at first that their eyes are more uncomfortable after Palming than they were before. This could be because they are now aware of the tension that was previously unconscious. It could also be a sign that they are trying hard to relax and Palm the 'right way', instead of allowing relaxation to occur.
There are many stories of people whose vision difficulties have been completely alleviated by palming. There are others, however, who derive only temporary benefit from the same practice. The difference is often in the degree of mental relaxation that has been achieved. The mind is part of the visual system. Since all the images of light received by the eyes are sent to the visual cortex for interpretation, in order for Palming to be an effective tool for healing, the mind needs to be engaged in a relaxing, enjoyable and absorbing activity at the same time that the physical eyes are resting.
There are as many ways to relax and focus the mind as there are people. Each person needs to discover what works, whether it is following the breath, imagining being in a beautiful place, remembering seeing clearly, imagining black, engaging in a vision drill which interests the mind and creates movement for the eyes, or listening to music, a relaxation CD or an audio book.
If you decide to imagine something in the visual field in front of your eyes, notice the distance at which you are seeing it, and whether there is movement in the activity. Play with varying the distance of the things you are imagining, looking at things both near and far away, and introduce some movement into the image. It is no more beneficial to stare blankly into the visual field in front of your eyes when you are Palming, than it is to do the same thing with your eyes open.
You can Palm whenever your eyes feel tired, or you can Palm as a regular practice. If you decide to Palm as a practice - like a yoga, meditation, piano or dance practice - you will probably, at some point, encounter some resistance. Part of you wants to do it, part of you doesn't. Palm anyway, and focus on connecting with the part of you that wants to and also with the part of you that doesn't. See if you can get a sense of what each of them wants for you. What purpose are they playing in your life? Let each part speak to you. Listen with interest and curiosity while you Palm, and be with all the parts of you that have something to say. By the end of the session you will probably have learned something new about yourself. It helps to meet and work with resistance rather than fighting against it or trying to make it go away. Accepting what comes up is more relaxing and beneficial than fighting it.
Whether you Palm for 10 breaths at a time, for 10 minutes or 10 hours, it is important to sense how you feel at the beginning of your Palming session, and check in again at the end. If you have an experience of calmness, of more clarity, or of any other benefit, remember it. Over the weeks and months you will become more practiced in being able to recall the feeling you get when Palming. This will be a great help to you in your life. You can ask yourself often: Do I feel as relaxed as I do after Palming? If not, either put your hands around your eyes for a few minutes in order to bring back the feeling, or simply remember the feeling. This can help you in developing a habit of noticing and releasing visual and mental tension before it builds up, and establishing a habit of relaxed aware attentiveness.