GUEST LIST FIRST! Sounds like sage advice to us:

It's not the most fun part of planning (and we'll be honest, it's one of the most likely to lead to a fight or two or twelve), but you shouldn't make any wed-day decisions before you have your guest list somewhat firmly in place. Why, you ask? Well, do you want to have a nonrefundable deposit down on that cozy restaurant room that fits 75 when your mother-in-law's additions bump your list up over 200? Exactly. Once everyone's in agreement, then you can move forward.

More thoughts from the folks at The Knot here.