Shipping products internationally can be very expensive as well as take a long time for them to be delivered.  There are a few things to consider when products are ordered from international customers in order to evaluate the best shipping options.  

The country where the product is being shipped is very important as the delivery time and reliability of deliver differs across different countries.  There are also different customs requirements you will need to take into account.

The product.  The size, weight, and value of the product will help determine the best type of shipping needed to reach your international destinations at the most cost effect, timely and secure rates.  The product will also determine the customs requirements needed for your product.

Timing.  Setting expectations for long delivery times on international shipments can help you reduce shipping costs but some items need to be received as soon as possible.  Understanding your clients' expectations can help to reduce shipping costs

With these factors in mind it is possible to estimate shipping costs and determine the best method to ship internationally.  Below are a few methods but depending on your needs it may be necessary to explore a few more.

Local delivery:  The most cost effective manner is to ship the products to the country of delivery and inject them in the local mail stream.  This saves money but many times the local mail systems is unreliable and can take a long time for delivery

USPS: USPS First Class Mail is another option which is more expensive but more reliable than local delivery.  For some countries the USPS will actually have better rates than inkjeting into the local mail stream and is often more reliable. USPS also offer expedited delivery but this can be very expensive

Carrier like DHL, UPS, and Fedex:  These carriers are usually more expensive but are more reliable and have options for expedited delivery.  Their tracking is also often more detailed and can get you a better idea of when the package will arrive.

International shipping can be very expensive and often times difficult to navigate but with the right information you have various options to work with and can expand your market and get your products to your international customers