Well the best I have been using is USPS. Its slower then other methods but it is cheaper for the Buyer. Another Downside is there is no tracking because the USPS does not work with other countries Postal Services. So your package is at the mercy of that Services reliability. You also dont have to worry about the buyer not paying their duty fees as they do have to pay it to get the item.
Fedex,DHL, and UPS are very expensive. Generally 2 times as much and more.