Yeah, from the US, USPS is the best option, the duties are the same, but Canada Post's fees, are a lot less.

As far as your responsibilities are concerned, just write out the customs declaration accurately, don't try to slide anything by. The actual duties and whatnot are the responsibility of the recipient, unless you choose to use a courier, and state that you are to pay the fees etc.

If it is from the states, and the value is under, I think it's $20, there are no duties.