I lived in Eastern Europe for a while and (thankfully was warned about this) when you buy flowers for someone always make sure it's an odd number. Even number flowers are only given at funerals.
Oh, and if you are introducing a friend of the opposite gender, make sure to refer to them a "colleague", the male and female derivatives of the word firend mean the same as boyfriend and girlfriend when the person is the opposite gender, the words mean friend when the person is of the same gender (yeah, I know, it confused me too). Every male I knew suddenly became my "colleague" or people would have thought I was a strumpet with multiple boyfriends
Woo boy, the intricate rules on greeting people in the Hungarian language took me months to figure out.