How to make sure extra people don't come to your wedding

Since I've had 3 couples in a row ask this question, I thought I would put it out there for everyone. I've been asked, how do we tell guests how many people in their party are allowed to come, or how do we make sure guests don't invite extra guests? The best way to do this is to simply write "We have reserved ___ seats in your honor" on your RSVP card. You fill in the blank according to your guest list, and it eliminates any confusion for guests (and wedding crashers!).