POSTAGE and Quantities: The number one tip you need when it comes to sending out your invites, is that your guest list number does not equal the number of invites your sending. Do the math on how many couples you have ahead of time, and you won't make the common mistake of ordering about double the invites you need.
RSVPS: Whether you choose to include a card for your guests to drop in the mail, a phone number to call, an email address to reply to, or a website to visit in order to collect your RSVPs, prepare yourself to have to hunt down more than a few people, regardless of your chosen method. We saved paper by only sending physical RSVP cards to our older guests (i.e., those who do not, and never will, own a computer or a smart phone) because we knew we'd have to chase down responses anyway. So we saved a little bit of money where we felt it might be thrown away otherwise. Here are a few more tips for collecting RSVPs.