I've never shipped anything internationally before. Help me!

I need to ship a PV kilt (not wool) from Texas to Victoria, BC, Canada. I'm going to use the US Postal Service, probably via Priority Mail unless there's a better option. Is there anything special I need to do to keep it from getting stuck in customs? Is the recipient going to get hit with duty fees or other nonsense?

I don't know how all this works, so please clue me in!