its a bit rng you'll learn the map little by little until you know where they all spawn outside of rooms, one piece of advice i guerss would be to drop any purple keys you find outside rooms if you can't take them with you, same for apples gives you a reference that you have searched that room and have no need to re scan it. Obviously don't leave the room if you hear a pred very close. (disclaimer: this advice doesn't apply at all in nightmare mode since key dropping makes noise and preds will b line to any dropped item location if they're close enough to hear it)