I read somewhere that one way to plot and finally finish a manuscript is to write the ending first. As a writer who continuously gets into trouble at the end of the story (not knowing how to end it), I can attest that this might be the way to go. My current idea for this year’s NaNoWriMo barely has enough of a beginning to call it anything but a passing whim. So, coming up with an ending seems a bit far-fetched (at least at this moment).
I have no experience yet with completing any of my WIPs (though I will definitely try this method), so I will leave it to the experts on explaining further. Here are some sites I found on writing the ending first. I hope they help. ^_^