Fair enough.
"Holding your hand up with the palm facing the person can be extremely offensive to some Greek"
Pacific Rim Asians also -- Japan, China at least. If you want to wave at someone, raise your hand with your palm facing you and pull your hand toward you as if suggesting "come here".
Also in Japan, when in doubt, smile! (Seriously)
I think many people in other countries do not expect foreigners to act like them. But, they are charmed if you try. Especially if you learn a few basic greetings in their language.