http://www.cbsa-asfc.gc.ca/travel-voyage/ifcrc-rpcrc-eng.html
http://www.cbsa-asfc.gc.ca/publications/dm-md/d2/d2-3-2-eng.html
Basically, make a list of your goods. Bring it with you on your first entry:
> 9. Prior to importation, former residents must prepare a detailed list in duplicate of all goods to be imported that indicates the make, model, serial numbers (where possible) and approximate value of each item. For general household items, a group listing and overall value is sufficient (e.g. kitchen utensils – $000). The list should be divided into two parts showing which items are accompanying the owner at the time of return and which items are to arrive at a later date as "goods to follow." This list must be presented to the border services officer at the first port of entry (POE) when the former resident arrives in Canada, even if no goods are being imported at that time. Instead of a list, Form B4A, Personal Effects Accounting Document (list of goods imported), may be used.
Be sure to declare it when you cross the border. This is what lets you import your goods without all the charges.