I would like to add that once you've faxed the paperwork to the broker, from the shipper, it is a very good idea to wait a few minutes, then phone the broker to ensure that the paperwork was received, and contains all needed info, before leaving the shipper. This doesn't guarantee a troublefree crossing, but it sure helps. Your carrier will provide the broker's name, fax, and phone numbers, and the shipper will almost always fax the paperwork from the office, before you leave. If they won't, or their fax isn't working, I'd go to the nearest place to fax, before accepting the freight - a problem at the border can be incredibly time consuming! Also, you can, and should, phone the carrier if you have any questions - they are there to help if you're unsure.
PS I have done a few FAST loads, and recently a CSA load, which was a breeze, and I don't have a transponder!