Many couriers will call ahead to make sure you are home and they do not waste a trip.
Many US sellers use couriers for domestic sales (to the USA) because the service is believed to be better than USPS.
If you give a number, make sure it is one where a message can be left if you do not answer.
BTW- If you are buying from the USA, do NOT buy from a seller who uses couriers internationally. There will be a huge fee to pay on your doorstep. USPS/Canada Post only.