A: There's no one exact way for all. How and when a person will leave his body and where he will go depends mainly on his guna and karma (joined with interventions by others through blessings, prayers, rites, etc.)
From accounts of dying persons and hospital staff coupled with the sastric descriptions (mainly Vedanta sutra, BG, Puranas) these things happen:
Several days/hours before death the person enters the terminal phase. O