I used to ship internationally almost for a living. So let me walk you through the steps and the pitfalls:
There are some countries I will not ship to, period, such as Italy. I even had a registered parcel go missing in Italy. Registered is no guaranty, it slows down the shipment, and filing a claim and getting paid can take a year.
The CN22 can only be used for low value shipments, and in general those weighing less than 4 pounds (1.8kg). It also cannot be used if the shipment requires or has a validated export license. Export licensing is something I am expert on, but that is subject matter that goes far beyond what this discussion can cover in a reasonable amount of time. If it weighs less than 4 pounds it can go as as a 1st class parcel. That is a double edged sword. You cannot insure 1st class parcels, and while it has tracking, that tracking ends where the parcel leaves the USA. That is something that the Post Office doesn't like to publicize. So for purposed of PayPal, it is NOT tracking because you will never confirmation it was delivered. The good news is that because it cannot be insured, the post office and Customs authorities rarely even look at the declaration, so the odds are that duty and taxes will not be charged. YMMV
If the shipment required or has a validated export license, my advice is use air freight, and live with the paperwork (shippers Letter of Instruction, Shippers Export Declaration etc). I suggest researching your export before you offer it for sale. You would be surprised at some of the things that require an export license. A few years ago I sold a 6 year old 100 Mhz Fluke Scope Meter to someone in India. Fortunately it turns out isn't really a 100Mhz scope. What is does is to take 4 samples, each slight offset at 25Mhz to create the illusion of 100Mhz. It turns out if it really was a 100Mhz device, it would have required a validated export license to India! Penalties for export law violations can be severe, and that is probably another reason many US based sellers are in no hurry to sell outside the USA.
If you exceed the permitted value for 1st class, you are going to need a real customs declaration. My advice is to do it all on line at
www.usps.com. The only thing you really will need to find out is the Harmonized Tariff Schedule number for what you are exporting. HTS listings are online. Just make sure you the export HTS number, not the import HTS number for the USA. Be careful. Picking the wrong HTS number can vastly increase the import duty. For example some years ago someone built me an HID flashlight, it cost about $250 plus shipping. Had it been declared as a flashlight, my recollection was the import duty to the USA was 30%. I had him declare it as portable HID lighting which was non-dutiable. Don't worry if the HTS listings seem confusing. They are, and there is reason licensed customs brokers make such good money. They deal with this stuff for a living. However many products may fit in more than one HTS number. I always picked the one with the lowest duty, and was never challenged.
However even if you do it right, you can still run into trouble. I shipped a replacement part to someone in India using a GLR (repair license). Under US Law, such exports are required to have a value of ZERO since you are replacing equipment under warranty. Unfortunately Indian Customs regarded that as fraud and seized the shipment. Federal Express accused me of fraud, and I reminded them the documents has been prepared in accordance with US export law, and if their customs representatives in India had a problem with my complying with US law, they had a serious problem. A Vice President of Federal Express subsequently apologized and acknowledged that the export paper work had been filed in accordance with US law. I never did get the part back however. It turned out I was the meat in the sandwich in a pissing match between the Indian Government and Federal Express's Customs Brokerage firm in India. I ended up having to report the seizure to the Bureau of Export Control because it was a licensed export. I have no idea what they did.
Know and understand what you are selling and shipping, and understand the regulations. For example you cannot ship Lithium-Ion batteries Internationally unless they are actually installed in equipment. Domestically Lithium Primary cells for devices such as flashlights and cameras may be shipped. I interpret that to mean CR2 and CR123's are legal, any primary cell larger than that is a probably prohibited. Lithium Ion cells may be shipped domestically both in equipment, with equipment. However you are generally limited to 8 cells or 2 battery packs per shipment subject to a 1.1 pound weight limit for batteries shipped with and/or installed in equipment. The parcel usually must also be clearly labeled stating that it contains Lithium or Lithium Ion batteries. See
http://pe.usps.gov/text/pub52/pub52c3_026.htm#ep929913
International shipping is far more restrictive. Lithium Cells must be installed in the equipment to be shipped International or to APO/FPO or DPO addresses. In other words, NO SPARE BATTERIES can be shipped either by themselves, or with the equipment. SEE
http://pe.usps.gov/text/imm/immc1_014.htm#ep1059904 . Global Express Guaranteed shipments (a type of EMS service) cannot contain Lithium or Lithium Ion batteries period.
It goes without saying that all shipments containing batteries must be packed carefully in boxes that are heavy enough to survived USPS handling.
Most International shipments must be handed to a Postal Employee, you cannot simply drop them in a mail box. Some post offices deal with International Shipping much more than others, and some are much busier than others. If you are unlucky, you can waste an hour at the Post Office mailing an International Parcel. Another reason many US sellers don't want to be bothered. Not all Postal employees are trained in International shipping, and as a result, mistakes in documenting and handling these shipments are embarrassingly common. I had a EMS parcel to Kuwait returned to me because a postal employee thought you could not send parcels to Kuwait. It turned out you could not send some types of parcels, but EMS was clearly permitted. It only delayed the shipment a few days when I took the parcel back to the Post Office, and brought a copy of the relevant Postal Regulations with me. I also remember watching a transaction, and when I got the counter, actually asking the clerk if the parcel he had just accepted was legal. It turned out it wasn't, it exceeded the size limits. It was returned to the shipper. So expertise varies enormously and this can lead to considerable frustration for the shipper.
The bottom line for US sellers is that International Shipping is expensive, time consuming, and often carries far more risk (that the buyer is unwilling to compensate you for) than a domestic transaction. The domestic market is large enough that the potential gain from selling Internationally doesn't adequately compensate for the additional time and aggravation involved.
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