In most cases, you wouldn't need to worry about additional costs for shipping items worldwide outside of the information your supplier provides. That said, depending on the type of product shipped, the item may be subject to "duty" costs when crossing the border. This cost is typically the responsibility of the customer once the package is delivered as duty costs are a way that the local government collects proper taxes.
These fees will vary from country to country, however, I'd recommend researching whether the countries you wish to sell to will charge your customers a duty fee. If the products you sell generate a duty fee for the countries you sell to, then I'd suggest outlining the possibility of duty fees on your product pages, or in your shipping section if you have one. This way you're being as upfront about the potential costs that your customer could incur.
If there's anything else I can help with please don't hesitate to reply back and I'll happily help out!
Trevor | Community Moderator @ Shopify - Was my reply helpful? Click Like to let me know! - Was your question answered? Mark it as an Accepted Solution - To learn more visit the Shopify Help Center or the Shopify Blog