i need to finish writing a novel that i have started. i have reached 15000 words and i'm stuck on how to continue.
Developing character, as suggested in the post above, is a great way to get more mileage out of ideas you've already got in hand. It's also necessary, usually, if you want to get an audience invested in the plot line.
Here is one sort of specific idea: Create a back-story meant to develop a single character and to explain this character's motivation within the context of the story you already have written. In the back-story, you can create a new set of plot points, albiet on a smaller scale than what you've got in your 15,000 word first draft. Not only will this add pages to your book, but it will also add interest and investment in a character as well as lending a greater sense of reality to the book as a whole.
History, even made up history, makes things seem real. So...add some.
A final and larger piece of advice would be to plan on writing more drafts. If you always plan on following up a first draft with a second draft and then a third, you give yourself the time, opportunity, and freedom to develop new ideas over the course of these successive drafts. When writing fantasy, there will almost certainly always be plot points, ideas, and characters that can be better explained and developed. Planning to do multiple drafts means 1) you won't have to explain everything fully the first time around and 2) you will give yourself a chance to identify the points begging for development and 3) give yourself the best chance of writing something really great.
Spend a lot of time developing each setting and character. This is where a lot of short stories and novels fall short. We should be able to picture each setting, and know each character. The more we know about them, the more we will care about them and what happens to them. Since it's a fantasy, the setting and characters may not be what we are used to either, so that's another reason we need them explained.
Is the word count a requirement that has been set by a publisher, or is it a goal that you have set for yourself? If the former, if you're really stuck and can't think of a way to get past your present point, then I'd suggest trying to work backward. That is, decide how you want to end the story, and write an outline of what it will take to get there. What plot changes need to be made? How do the characters need to develop? You might shake your imagination loose by doing this. If, however, the word count is a goal you set for yourself, then I'd suggest setting a new goal. You'll finish when you're finished. Let a publisher tell you that you need to add a chapter or scene.
Experienced writers always warn new writers that the middle is the hard part. To get past the boulder in the road of your thought and progress, you need to logically extend and expand what you have in the first half. If you have subplots (characters other than the main ones who have their own life stories going on--or--secondary problems that the central characters have going on), some chapters will definitely be devoted to the problems, personalities, and complications going on there. Many authors alternate chapters in some fashion between main plot and subplot(s): e.g., main plot, subplot, main plot--or--main plot, main plot, subplot. Also make sure you have the actions of the plot worked out well enough: this happens and this happens then this happens and this happens, etc. Aristotle says action (plot) construction comes before character construction, but some disagree and advise that well described, detailed characters result in plot action. Either way, answer what happens next and you should be able to move that boulder in the road.
The first thing I would suggest is to forget about the word count. For me, I can really restrict myself if I start worrying about the length instead of the content. I find it helps to just write everything that I want to write first (which usually exceeds the number of allotted words). Then, I can narrow it down or edit it to fit the word count I need.
You might also find it helpful to do some plot charts or story boards. See where the story is going or where it can be expanded. Maybe you will want to be more elaborate in describing the setting. After all, in a fantasy story, the reader should have little knowledge of the setting. Or maybe you will want to be more elaborate in the character development. It really depends on what you want your story to be like.
In writing a fantasy novel, your goal is to create a whole new universe, filled with new characters and situations. Without knowing what your plot is or what you've written so far, it's difficult to give specific suggestions but here are some ideas to consider.
Because you are creating a completely unfamiliar setting, have you provided a complete description of your new world and the characters in it? This is an opportunity for the most colorful writing you can use as you paint word pictures allowing your readers to envision the places and characters and actions you are featuring in your novel. You may be able to add to your word total by supplementing what you have already written with further in-depth detailed information.
Would it be possible to add more challenges to the plot of your novel? In a fantasy world, you have the liberty to insert complications that would not be a problem in our world or to make up completely new circumstances that would impact the rising action. Again, make sure you are providing enough descriptive writing to enable your readers to be drawn into the action.
Adding more characters would be another way to add more words, as you described these new individuals and explained how they are related and involved in the overall plot.
You've set quite a challenge for yourself - good luck!