How can we make sure that guests are clear on whether or not they can bring someone with them to the wedding?

If you're sending a single invitation to multiple people, we strongly recommend that you address your invitations with each individual, specific name vs. "and guest" or "and family." This will help make it clear which people are invited, and if there are any changes (like someone breaks up with their boyfriend or something), you'll be less likely to have random people coming to your wedding.