Writing Placecards

Ok. If you have a couple are you suppose to put:

Ms. Christine Smith & Bob

Or are they suppose to have separate placecards??

Also, if they are married do you leave the husband's first name out

Mr. & Mrs. Doe

What happens if you have two people that are married that have the same last name? I guess put the first initial?

Put:
Mr. & Mrs. First Last

you usually will have a few couples with the same last name because they are family, so you need the first name as well.

For single people bringing a guest we did:
Mr. First Last & Miss First Last
or
Miss First Last & Mr. First Last
[depending on their relationship to you]