[insert techno music] On March 30, your Facebook brand page will automatically switch over to the new "Timeline" format.
As John Haydon has pointed out, you shouldn't panic about this; it doesn't change much in terms of how your users interact with you. It is, however, something to be aware of, and to prepare for, so here are the top three things you should do to get up to speed:
1. Say goodbye your default landing tab. With the change, Facebook will no longer allow you to select a default landing tab for your page. It's all-Wall, all the time now, so re-evaluate your strategy and consider how it might change your approach.
2. Get a cover photo. If you want to crop a photo just-so before uploading it, the dimensions are 850px by 315px. (Also, be aware of what Facebook's rules say you can't do with cover images.)
3. Consider pinning. Not in the Pinterest sense, but you can "pin" a post to the top of your page (probably the closest thing you'll get to that default landing tab).