Do Pranayam (Yogic Breathing), sit still and in a straight posture concentrate, and try to conceive the formless. Progressing in 'Kriya' and seeing all during (in) 'Yoni Mudra' by abandoning all desires and not letting any desire overcome you, if at all anything , any wish any thought enters you, drop it naturally, and meditating with a clear mind reach there where there is no Sun, no Moon and no fire flame, but still all is visible. (YOGIGURU SHREE BHUPENDRANATH SANYAL)