Hindsight Tip #1: Verify your guests addresses. A few of my invitations were returned. I had the wrong address. Wish I had just picked up the phone and called my guests. Or better yet, delegated this task to a bridesmaid or mom.
Hindsight Tip #2 Have the Post master check your postage against an invitation's weight: I felt pretty clever to have asked the postmaster to weigh my invitations before sending them off. They were too heavy for the standard postage and required and additional stamp. This is tip #2: Make sure to have the postmaster weigh your invitations to ensure that you have the correct postage.
Hindsight Tip #3 Send yourself a test piece: The envelopes that were returned looked like they'd seen better days. They were mildly mangled on the outside. On the inside, the sweet butterfly that secured the paper wrap was broken–too late to reinforce them. I wish I had mailed myself a test invitation so I see any damage or issues with mailing them. In hindsight, I would have reinforced the butterfly and paid more attention to matching my envelopes to my invitation.