Unaccompanied Personal Effects
You need to import those items as "Unaccompanied Personal Effects".
When you cross a border with checked baggage, it is assumed that all of the items in your checked bag are your personal effects unless you specify otherwise on the customs declaration form (e.g. USA, Japan, Canada) that you fill out just before entry. Accordingly, by default you are not required to pay any duty on your checked baggage.
On the other hand, when you courier items across a border it is assumed that they are commercial items and you are typically required to declare their value to the destination country. Most countries will grant you an exemption to import duties for Unaccompanied Personal Effects. The key to getting the exemption is to attach to your couriered package the following items:
The easiest way I have found to get the forms for the country to which you are importing is to use the Fedex workflow for shipping (Purolator, UPS, etc might have an equivalent). The Fedex workflow produces the pro-forma invoice with all the appropriate declarations and fields filled out, and points you to the appropriate unaccompanied goods form for the country. Make sure you sign and date the commercial invoice and the declaration form. It is conventional to include 4 copies of all the paperwork on the outside of your package, and another one on the inside of the package.