Tips for successful buying on Ebay
First check the sellers feedback. Most bigger sellers have excellent feedback ratings. Do not buy from sellers with poor feedback ratings. The sellers I recommend are very friendly, keep good contact and give good service.
If you have any questions, mail the seller. I often mail the seller during the auction to find out if he/she responses fast. Most sellers are very friendly and helpful, professional as well as private sellers.
If you live in an other country then where the seller lives, and he only sells national, just ask. I live in the Netherlands, and have bought lots of G-Shocks and other stuff at seller of the U.S. and Germany that sold nationally. If you just mention you will pay the extra costs for international shipping, most sellers have no problems selling it to you.
If you see a interesting G-Shock, check if it is not a fake (check the Fake section). Most important is that it's a Casio Watch. Most models have the name G-Shock written on the case, some on the dial.
Get a Paypal account. It's the fastest way of paying someone internationally, and most sellers accept Paypal.