Just something I found out the hard way today...
We finalized our RSVP's about two weeks ago, my wedding is next weekend. We had to give our caterer a final count a week ago, so we did. Well, now we hear so-and-so isn't feeling well and won't be able to make it (we totally understand), and so-and-so has a last minute work function they can't miss or they'll lose their job (again, we completely understand).
But what that means is we're paying for about 4 people more than will be in attendance.
So - my advice is to UNDERESTIMATE! Most caterers will gladly add up to the final number, no problem. But once you give them a number, they won't go under that. In retrospect, I wish I had cut off about 5-8 people from my number (about 5%) knowing that there would probably be some no-shows and some last minute cancellations so we wouldn't have to pay for them.
Just a word to the wise for those of you later in the month!!!