Xpresspost USA and Expedited Parcel USA:
Name, address and phone number of sender
Name, address and phone number of recipient
Non-Delivery Instructions - (Return at Sender's Expense or Abandon)
Reason for Export (Gift, Sale,Document,Repair/Warranty,Commercial Sample, or Other)
Quantity,Detailed Description of Contents, Net weight, Declared Value in Canadian Dollars
I never bother with the net weight. They do that anyway when I take it to the post office. I also usually fill out the country of origin and HS Tariff No. from the Commercial Senders section to help avoid confusion.
I have no clue if any of my buyers have been dinged with duty, taxes, etc. I just warn that it is a possibility. I never send UPS or Fedex, as I am working under the assumption that they are doing the same sort of charges on CDA>US that they do on US>CDA