Timing of the prashna have to be chosen on astrologer’s behest and the time when native utters/write questions to an astrologer have to be taken as birth time whereas the time where question came in mind is taken as conception time.
Prashna is a fabulous branch of Vedic Jyotish which proves that each and ever movement of human life even thoughts are controlled by planets. For casting a prashna chart Birth Details are not required only time when Native approaches an astrologer in Required. Prashna is generally effective for one year only whereas with some special techniques or in some special questions more than one year can also be predicted.
To have a Prashna reading please be clear about the question, write it clearly without confusion, along with that write a number between 1 to 108 after mental prayer to god. Best advised is to chant guru mantra “Om Gurave Namah” 12 times mentally to have clear guidance and number that will lead astrologer to guidance and results.
Prashna is best done while sitting in front of an astrologer but for those who can’t meet it can also be done using other means.