Sending cards is a nice way to mark all kinds of occasions but a few guidelines of etiquette do apply. Hallmark offers the following suggestions: - When sending a card to a couple with two different last names, address the card to "Mary Smith and John Jones." If there are children, write "Mary Smith, John Jones and Family."

- Some divorced women use their maiden names. Make sure you know which last name and courtesy title (Mrs., Ms. or Miss) she prefers.- Family signatures begin with the father's name, then the mother's and finally the children. Cards also may be signed "John, Mary and Children."

- If a card is from more than one person, the person who signs it should write his or her name last as a gesture of courtesy.

- Personalize your cards with a little note and always sign the card - even when the name is printed.

- Keep your signature informal by using no courtesy titles. When sending a card to close friends and relatives, use only your first name.

- Remember, a Christmas card should be much more than a mere social gesture. It should be a personal communication to express sincere good wishes.