There are a number of preparations to make to have your body in a state to get the best possible results from your mantra meditation practice.

If you practice some form of mind body physical discipline such as tai chi or yoga it is a good idea to do this before mantra meditation practice so that the body is warm.  If not, do your practice in the morning after showering and cleaning.

Posture is one of the core elements to a successful mantra meditation practice.  Aim to position the spin for it to be in natural alignment.

Sitting postures that are ideal are the cross legged positions.  On this posture there are a number of variations.   For the flexible there are the cross legged variations such as the lotus and half lotus postures.

Use cushions, bolsters and mats and whatever you need to make the position comfortable.  The secret to the cross legged positions for correct spinal alignment is to tilt the hips forward.  To achieve this sit on a cushion with legs on the floor.  The hips will naturally tilt forward slightly in this position.  This naturally puts the spine into alignment.

For those who have difficulty with this position there are alternatives.

You can try the legs folded with shins parallel to ground and sitting on your feet position.  Use cushions if you need to make the position more comfortable.

There are alternatives for those that have mobility problems and find sitting on the floor difficult.  Find a chair.  A hard chair is preferable.  Sit up straight with the spine in alignment in the chair.

Remember that you should never put your body in a position of serious discomfort.  This is not the objective of a mantra meditation practice.  It is essential to always listen to your body and in finding an aligned spine work with a position that is comfortable.

The purpose of the aligned spine is that it positions your body, mind and energetic centers in the best possible position to focus on the mantra meditation practice itself.  This helps you to maximize the results of your mantra meditation practice.