There are many approaches to meditation with various forms used. Sometimes a person says something like "this is the only correct way". I have found that there are certain elements which are basic to the forms, and toward which they point. They are balance, stability, and relaxation. This is so a person does not have to use effort to hold up the body or parts of it and can forget about the physical level. As a result of that, one generally finds that the position ends up being straight spined with the head on top, the shoulders and arms relaxed, the feet flat on the floor and spread about shoulder width if sitting in a chair, the hands in the lap or on the legs.
Can there be other approaches or forms? Sure. One can meditate from any position. Meditation is a state of being or consciousness. It is not dependent upon form. A person can lay down, stand up, walk, sit, etc. Each one of those forms has its particular potentials. For the sake of this writing, I will stay with sitting.
The main thing it to give yourself a chance to develop the position and form that works best for you. To give yourself the chance, by paying attention to the penetration and flow of energy, breath, and life - and your awareness, quietness, consciousness, focus to adapt from the inner outward in a way that the form you adjust to promotes the experience. In this way you will find yourself taking on the "proper" form for the process. Make the adaptations and adjustments to promote the free flow of life, breath, and energy. Wherever you find tension or a blockage or constriction of flow and penetration, make the little adjustments in your body to release the tension and let the flow, breath, life, and energy penetrate and increase. You will probably fine, interestingly, that eventually you will come to a position which closely represents a so called classical form. However, you will develop it from the inside out, from you own experience as to what works best for you.
Find a quiet and comfortable place to sit. I suggest a chair - not too soft, and preferably straight backed. If you prefer to sit on the floor on a cushion with crossed legs, or a flat mat and are comfortable in a lotus position that is fine. It is not so much where or how you sit but rather that you are stable, solid, and able to relax. It is more important that your back be straight, with your head balanced on top of your spine, not drooping down or sagging on one side or the other. Your hands can be on your legs, in your lap, or crossed. Your eyes can be closed, open, or partially open. Relax and start with what feels easiest for you. You do not have to be in a room with no noise or distractions. Just don't dwell on them.
Try to let go of any tension that you feel. Don't try to force it away, just what you can drop away. Now put your attention on your breath. Breathe in and out through your nose. If you need to breathe through your mouth then do so. Don't worry about it. Try to relax your diaphragm so that you "breathe through your belly" rather than have your chest expand. In other words, let the lungs sort of drop down instead of pushing out your chest. This takes a little practice to get the hang of, so try it, but if you have trouble with it, don't worry. Do it a little each time you sit and it soon will become easy.
Experience the qualities of breath. As you sit, let go of tension and let your body readjust to its most comfortable positions in which the breath can "flow" through it. You then start the object of the concentration or meditation. After several days of doing this you will begin to feel that this is natural and more easy.