I'm sure this has been asked hundreds of times but I didn't think about it until tonight.
My Fi and I have decided to only add "and guest" to wedding invitations for those people in serious relationships. Tonight I went to dinner with a friend I hadn't seen in a long time and this friend is currently single. When we started talking about the wedding she said "I'm so excited! I wonder who I should bring as my date?" It totally caught me off guard and I just kind of took the easy way out: laughed and change the subject.
In this case I've decided just to not bring it up again and hope she assumes she can't bring a guest if only her name is on the invite but how do I handle this in the future? This situation is a lot harder than I thought it would be because I've always been one of those people who's like "just tell them!" but I chickened out!