How to I ensure my invitees do not bring along uninvited guests?
The etiquette is the envelope is king. If you do not want your guest to bring a date, simply put "Mr. John Smith" on the envelope. If a date is acceptable, write "Mr. John Smith and Guest". They should get the hint. If, for some reason, you think you have a large amount of guests that do not know or won't abide by this rule, you can try the more direct approach on your RSVP card. Have your invitation designer add a line that says "____ seat(s) have been reserved for you". Before you send the invitations out, fill in the number of seats the guest should expect and leave it at that. Lastly, to add my two cents onto a very cut and dry question, please remember that while it is your wedding day, you are also entertaining your guests. A good host will always keep their guests comfort in mind and if allowing your guest to bring a date to the wedding is within reason for your venue and budget, please consider encouraging this. After all, think about how comfortable you would be if attending a wedding, party or dinner without a date.