Tips on getting guests to return RSVPs by deadline?

[shawnswoman]

As you can see from my signature line, our wedding is months away still, so I probably shouldn't even be worrying about this yet. Reading others' posts regarding guests failing to return their reply cards has gotten me thinking about this dilemma, though.

Because of the place where we are hosting our reception, I must provide a firm count of guests 30 days before the wedding. If the count is underestimated, guests will literally not be able to be in the same room as the reception; if I overestimate, we will be charged extra. So I really need to have an accurate guest count by just a day or two after the RSVP deadline.

Anyone have tips on how to get guests to RSVP in a timely fashion?