List of faux pas - Wikipedia, the free encyclopedia
Czech Republic and Slovakia

* It is considered mildly impolite to wear baseball caps inside. [citation needed]
* Women's last name tend to carry the appendix "-ova". For example Mr. Johnson's wife's last name would be Mrs. Johnsonova. Addressing a man with a female form of his last name (e.g., Mr. Johnsonova) is a serious faux pas. [citation needed]

Useful tidbits from Wikipedia. Bohemica has a more extensive list here.