Pranayam means “control of the breath” and it is a wonderful form of meditation. Essentially, one should breathe and hold it, during any exercise this is beneficial. If one is walking, the longer one holds the breath, the better. During more strenuous exercise, this is helpful…

Mantras are always helpful, but in pranayam, the final goal is beyond all mantras.

As in most cases, it is most important to have good karma before meditating.