Note the size of the private letter. A large sheet of paper may have to be folded several times to make it compact for hiding. Letters with several pages will require a larger hiding space. Keep the letter in an envelope to prevent it from deteriorating or becoming ripped.
Hide the letter in a bedroom or bathroom rather than a communal area, such as the kitchen or living room.
Make space for the letter in an existing piece in the room, such as a slit in the mattress or cushions, inside a book or behind a wall clock. Nothing should appear out of place.