Canada Border Services Agency (CBSA) maintains a robust, user friendly website. Here are several links that may be helpful for traders:

https://www.cbsa-asfc.gc.ca/agency-agence/program-eng.html

https://www.cbsa-asfc.gc.ca/export/guide-eng.html

https://www.cbsa-asfc.gc.ca/import/guide-eng.html

https://www.cbsa-asfc.gc.ca/import/courier/lvs-efv/menu-eng.html