Mark Lev:
I'm not very skilled with the formless jhanas, but intuition tell me that Nirodha Samapatti would be a useful thing to master eventually.
Well, in that case, in order to arrive at
sannavedayita-nirodha (the cessation of perception and feeling, also known as
nirodha-samapatti) you would have to have traversed through the four formless absorptions. So, you may want to give some attention to their practice before attempting to go after the former.
While this cessation can be brought on by making a resolution beforehand (i.e. before entering the meditation session itself), my personal experience with it was that it occurred spontaneously one day as I endeavored to quiet the mind and reach ever more tranquil regions after the eighth jhana of neither perception nor non-perception.
You won't know it has occurred until
after the meditation as you review your session. It is perhaps something that all meditators are fascinated by, but after having experienced it once, I've not been attracted to it on any kind of regular basis. It is good to know that one can achieve it, though, as it confirms the depths of tranquility to which the mind can sink, as well as to confirm its reality from the standpoint of its being something taught in the Dhamma. There's nothing like a direct experience to confirm the truth of the Dhamma.