They explain why they can't put packages in your mailbox, and suggest that if you designate a location with a sign, that's the clearest way to get your package where you want.
They don't see delivery instructions until they arrive at your house, so "call ahead" type instructions are unworkable for the drivers. They also caution that the delivery vehicle might not be a branded vehicle, and that items may be visible when delivered, so if you want to surprise someone, make sure they aren't at home, I guess for the whole day of the delivery.