modern save the date

They are not required. 

They are actually a fairly modern invention, and are not required.  If you are having a wedding in your hometown and most guests live nearby, you may not need a save-the-date.  They come in handy if you are having a wedding during summer or on a holiday weekend.

They should be sent out about 3-6 months prior to your wedding.

Save-the-dates don't serve as an invitation substitute, so they should go out far in advance. Err more towards 6 months for destination weddings that might require greater cost or vacation time.

Be as creative or as simple as you like.

Save-the-dates don't need to refer to your theme or colors.  You can send out anything from a simple black and white note to a fabulous magnet of your engagement photo.

Solidify your guest list first.

You should never send someone a save-the-date that won't be receiving an invite.  So, make sure you've made your list and checked it twice before sending any save-the-dates.

A save-the-date shouldn't come with a RSVP request.

Guests don't RSVP to save-the-dates. That's for your invitation, so don't freak out if you don't hear from anyone.