I won't have much to offer but I started a fantasy story back in '05 and still haven't gotten anywhere with it (I've since started approximately 10 more stories, but still ;p )) and I keep thinking of how fun it's going to be once I do start into the "details" of the world!
So even though this isn't really the advice you're looking for, my best advice is just have fun with it! Free your mind and let your creativity flow.
Sometimes it just takes some reaffirmation to get it up and running. ;p
And also, I'm reading a book called Worlds of Wonder by David Gerrold. Have you checked that one out yet? It's written by a fantasy writer, sort of a "how-to" on fantasy world writing. I haven't gotten too far into yet so I can't say too much about it, but so far it seems interesting and promising! ;p
Have fun! I'll look forward to occasional updates about your story.