I need help with wording for envelopes!!!

Do you write mr. and mrs. John smith, or in the case of not being married do you write mr. john smith and guest on the outside, then just mr. smith on the return?

I am confused?

Thanks!!

in response to your question..

If they are married

Mr. and Mrs. John Smith

if single

Mr. John Smith (outer)

John Smith & Guest (inner)

Thanks!!

Okay so married guest I understand but if they are couple's do I put them both on the outside or just one and then both names on the inside?

This whole thing is confusing me!!

Married couples (OUTTER ENEVELOPES):
Mr. and Mrs. [Husband's First Name] [Last Name]


Married couples (with different last names) (OUTTER ENEVELOPES):
Mr. [Husband's First Name] [Last Name] and
Ms. [Wife's First Name] [Last Name]