Make sure to send your save-the-date cards at least 6 months in advance of the wedding to give people (especially those from out of town) enough time to plan. You should always include: the date, location, accommodations and your website if you have one so people have all the details they need.
I think it's important to have fun with your save-the-date cards. You can give people a little taste of who you are as a couple and get them excited about your upcoming nuptials.
Here are some great options:
DIY Vintage Postcards
Number Ribbon - too cute!
Handkerchief - such a unique idea!
Simple with blocks or color
Have you ever gotten a unique save-the-date card?