Need Help Addressing Invites

The correct way to do it is to address the outer only with the person you are inviting. If it is a couple living together you put both on the front. Inside you put both names on the inner envelope.

Very cool and the guests wanted more they even took ours.

For a single guest, do you address the outer envelope "Mr. John Smith" and the inner envelope "Mr. John Smith and Guest" or do you put the "and Guest" on the outer envelope as well? Or do you even have to put anything on the inner envelope?? The last couple of wedding invitations I received, they did not have anything on the inner envelope.