Perhaps that is the problem? That you're writing too far ahead? Maybe you should try writing their pasts before their 'present'?
Another way is to figure out where you want the story to go. A way to think about it might be to ask some questions. How will this event effect this character? How will that character respond? Have they experienced something like this before? How will this make the character grow?
As far as an overarching plot, try brainstorming. Just take a moment to let your mind completely wander. Back in school I used to take the city bus every morning to my high school. I came up with some of my best writing ideas on that bus. Right before you go to sleep, just let yourself think freely. In time you'll figure it out. Be patient and be open to new ideas.
Try keeping a notebook by your bed. Just let your mind wander. Close your eyes and imagine your characters. Imagine what you want your readers to experience. Write quick notes about it so you don't forget.
A lot of the time if you have trouble figuring out the plot, try working with the subplots. The smaller stories beneath the larger one.
Sometimes when I go to write a story all I have is one scene I really want to do, and the rest of the fic bubbles from that. "The Divine Champion" started with a scene with Paarthurnax, and alternate route for dealing with him. Instead I ended up with a huge, multi fic series.
Pick those scenes. Build around them. Write them if it helps, it might.
Being organized can help too. Try writing outlines, list of what happens in each chapter, major events and such. Try to make sure that each chapter has at least one main point, one further step to make it to the final resolution. To keep readers interested.
Another way, especially for fanfiction, is to experience the inspiration again. Watch the movies, read other fic, read the books.
Just came to say that I haven't dropped my fanfic, I just haven't had a chance to work on it. It's towards the end of the year and I've got finals and a load of projects that I've gotta worry about. It'll be a little bit before I continue.
Well, I just realized that your preferred method of contact was set to PM....Sorry about that. I was looking at another beta reader as well and that's where I saw VM in there. I got the two of you mixed up.
Hey, I just looked through the Beta Reader thread and saw that you were under the "Comprehensive Beta Reader" category. I'm currently working on a fanfiction of my own, and after having read your work, I'd figured that if you were willing, you'd be the best choice as my beta reader. So far, I'm only on the Prologue and that's not even finished, but I've decided that it'd be best to have someone look over the few pages of work that I've already finished so that I can fix what I have before I go too far.
Anyways, you willing to help? If not, I'll go ahead and contact one of the other Beta readers.