How often and for how long do you sit?
I've been doing the jhana practice as taught by the Venerable Pa Auk Sayadaw since December 2009. I went on a retreat that Tina and Stephen, the authors of the excellent “Practicing the Jhanas”, did on this practice over the summer at Cloud Mountain Retreat Center. While I have not yet attained jhana, perhaps I may be of some benefit.
The nimitta in this practice which appears visually to the mind’s eye (as gray smoke, cotton wool, light, “like the morning star”, etc) arises specifically as a result of following the breath at the anapana spot (i.e., beneath the nostrils or above the upper lip. They stress that when undertaking this practice you should use only these instructions and set aside any other jhana practice techniques you may know about. The breath and then the anapana nimitta (or later the white kasina nimitta) is the only thing you take as object; you never change the object or take one of the jhana factors as the object. There are other types of nimittas; Ian discusses them in another post in this thread.
They also note that there are no short cuts or big breakthroughs in this practice. I can attest to that; it often feels like a 3 step forward, 2 steps back (some weeks 2.85 steps back). Some even question the efficacy of this practice to achieve jhana outside the retreat environment, although I remain convinced that it can be done for no reason other than my own steady, albeit at times glacially slow, progress.
I have found that the key to developing this practice is to sit more and longer. I had to extend my sittings over 60 and 70 minutes to really begin to get deeper as opposed to just getting quieter at the same point. They talk about the awareness of the spot becoming an energetic knowing of the spot. This seems to go hand-in-hand with vicara (sustained thought) locking on to it. At this point there is what I call the “Closing the Car Windows” effect ; it’s like that moment when the car window shuts completely and there’s that immediate muffling of the outside sound. These points seem to really require one to letting go ; this “receptive effort” (p.64) is something I’m still working on.
You’re able to stay with the breath (vicara) and some bliss (piti), but no nimitta. Perhaps longer sittings might make a difference.
The authors also have some great talks on the subject at their website,
www.jhanasadvice.com, that make great listening for commuting and going to the gym.
I hope this helps.