Yes, even before you arrive at the wedding ceremony, you can make mistakes that can drive an engaged couple crazy. Luckily, it's pretty easy to avoid committing these offenses. Send in your response card late -- or not at all. If you receive a wedding invitation with a response card, make note of the reply-by date. It's usually a few days to a few weeks before couples have to give their final head counts to venues and caterers. If you don't return the card, expect a call (or a text or an email)...