For what it's worth, my advice would be to do a bit of buying on eBay first, in order to build up some positive feedback (preferably above 10). Buyers -- particularly overseas buyers -- may be hesitant to purchase from a seller with low or zero feedback. Take it from me, selling to North America can be a challenge, selling worldwide is even more so. If I were just starting out now, I'd restrict sales to Canada and the U.S. for a period of time until you get your "sea legs". Depending on what you sell, the vast majority of your customers will be in the U.S. or Canada anyway.
Also, as you may be aware, there are some restrictions imposed on new sellers. If you haven't reviewed those restrictions and other seller policies, it's a very good idea to do that before you start.
You need to do absolutely everything possible to make every customer happy and avoid even minor problems during the first few dozen transactions, as even one transaction gone wrong early on could seriously impact your ability to sell. Buyers don't like to see negative feedback or low DSRs for a seller with a lower feedback score. Start out slowly and carefully, and build your reputation buyer by buyer on familiar ground rather than trying to cover the whole world in the first few months.
You'll see comments on this discussion board regarding Paypal holdbacks for new sellers, etc. which may be helpful to read.
As the other poster noted, you can set your country restrictions ("ship to" exclusions) when you prepare your listings, and remember to set your shipping options to match.
Just a few notes of advice which I hope will help. Best of luck to you!
