How can I obtain a TN visa as a Canadian?
You must provide the following at the port of entry:
• A request for TN status
• A copy of your college degree and employment records which establish qualification for the prospective job
• A letter from your prospective U.S. based employer offering you a job in the U.S., which is included on the professional job series (NAFTA list) and
• A fee of U.S. $50.00
Note: Canadian citizens are not required to obtain a visa, but instead receive TN status with the USCIS at the port of entry.
http://faq.visapro.com/TN-Visa-FAQ2.asp