Packaging And Embellishments: If you're adding embellishments, or you're mailing more than just an invite plus an RSVP card (we opted to mail more info, because of the destination aspect), keep track of the weight of your invitation suite once it's all packed up. Depending on its size, you may be facing more postage fees than a simple stamp will cover. You can get a postage estimate using a kitchen scale and checking on the USPS website. Through the USPS website I also learned that square invites and envelopes cost more in postage, by a significant amount. It's not worth it.
ADDRESSES: You can choose to address your invitations by hand, or you can decide to print labels. Don't let the WIC bully you into thinking your own handwriting isn't good enough, or that the convenience of labels is tacky. As for the actual addresses, here are a few tips on how to address invitations formally, accounting for a whole host of last name conventions.