Having trouble starting a fantasy story...?

Plunge right into the action -- without any sort of development -- then develop that. I am quite serious. The secret of an exciting opening is that you start in the middle and then bring the reader up to speed. Also show don't tell, but that means find something in the situation where someone is DOING something, and SHOW them doing it. Don't EXPLAIN them doing it -- yet. You should be able to make it clear what is going on later.