Like most questions asked on this board there isn't an easy answer.
It depends on circumstances.
Paperwork?
Will you be leased to a carrier?
Is the carrier FAST approved?
Will or are you be FAST approved?
The carrier, if you are leased to one, will provide you with PARS barcode stickers that you must affix to the Customs invoices prepared by the shipper. You must then fax those to the correct Customs Broker at the correct port where you will be crossing. You must send these a MINIMUM 2 and a half hours before you arrive at Customs.
That is the basic procedure.
Is that the information you were looking for?