Rats! I read a thread about this about a year ago on another forum, but neglected to save it (or remember where). With the right google-fu you should be able to find some good tips.

We get requests to "Ship as Gift" from customers all the time on a site that ships international.

All that we've done is clearly mention in as many places as possible that fees are the responsibility of the customer for international orders. Normally, an international order will get some extra attention (more often than not there is a pre-sale inquiry from customer asking if we ship overseas) and fees are explained and paid by the customer (like Aaron mentions). Haven't run into any major snags doing it like this. Would be nice to be automatic, but as to how that could happen is beyond me...LOL..

Or when a customer refuses the shipment, you still have to pay the courier fees, which is what customers balk at.

I switched to only allowing USPS for shipments to Canada. If a customer would refuse and I get a notice from USPS that I have to pay customs, I would reduce that from any refund sent to the customer.