This is a tough question because there is SO MUCH to look at and new opportunities/ideas are being developed every day. At the core is DEVELOPING RELATIONSHIPS. That is foundation for the whole site and has to be kept front and center to help build your brand on the media. Really the core of radio promotions and brand marketing has always been about developing a strong relationship with the audience. We've done it on the streets with promotions, over the air with our imaging, personality, and audience interaction, and we also do it through the music formats we build.
As we venture into Facebook we really don't know what works. Should we be developing games, posting videos, tagging pics, telling jokes, showcasing artists we play, polling, running ads for clients, or letting the audience interact with us? Maybe we should be doing all of this, but that's a pretty daunting task. We need to look at what the audience wants in a radio brand relationship?
Maybe the place to start is by looking closely at the pages of your 'friends' or 'fans' on Facebook. Now you can't access the pages of the people that just 'like' your page, but you can build a panel or 'focus group' of fans. You can invite people to be 'super fans' of the station and 'friend' them on another site where you perhaps can offer some freebees or other incentives. Here you can look at up to 1000 people and see what else they like, what topics and features they react to and also learn a little more about them.
Another trick here is to simply keep track of what you do on the page and what the reaction is. Keep a daily log on a spread sheet and you'll see what moves the 'likes' up and what got the FB audience moving. Here is a rough example that you can build on with your own tracking fields: