A buffet and hutch is a two-piece dining set: a heavy lower cabinet and an upper display shelf. The single most important step is separating the two so you are never wrestling the whole tower at once.
Pro tip: Note how the hutch attaches to the buffet before you separate them, since the fasteners are often hidden behind the back lip.
Watch out: Do not try to move the buffet and hutch as one unit; the top-heavy combination can tip and the connection point is not built for lifting.