Billions of greeting cards hit the mail each year around this time, and it is possible many recipients have either moved homes, gotten promoted, married, divorced, or died. There are common etiquette and grammar mistakes to avoid when addressing cards on your holiday mailing list. What do you need to know? Etiquette expert Sharon Schweitzer from Access to Culture offers this advice: Titles: Unmarried Women Miss: Historically, used for young, unwedded women. “Miss” is used until age 16 to 18. Today, this is still used in certain social circles. Ms.: Used as a default form of address or when unsure if she is married or not. Unwed couples living together: Use her maiden name, such…