for me typically the side closest the door (but i end up in the middle of the bed), the door 75% closed with an item that will be knocked over if opened and make lots of noise. (also one and each door entrance that will be knocked over if opened without causing obtruction but lots of noise) comes from boarding school days.
Ever since i have had my own place, all my own pets never let sleep in my room, they never allowed to cross the threshold. i have asthema and so hairs on bed is very bad. they did however have lovely soft sheep skin beds with fluffy blankets for winter.. and tooo see them climb in and either wait for me to cover them or flip it on themselves was too dam funny.
since my divorce i had to give up my pets, miss them dearly.