The biggest ingredient is effort.  I say that now so that it doesn’t get forgotten.  Write every day.  Be consistent.  Put in the effort.

You’re ready to put in the effort – ok, here are a few other pointers.

1. Tell a story.  Don’t build a world.  This is not a Dungeons and Dragons game you are about to run.  Nobody is really that interested in the torrid details of your world.  Yes those details are important, but not as important as the story.  A story has a hero, an antagonist, a love interest – all those things that we enjoy reading about and watching in the movies.
2. Show your story, don’t tell it.  You have a love interest and a hero.  Don’t say “and he fell in love with the princess.”  That is kinda blah.  Rather show his/her actions and words as they interact.
3. Write your story.  All too often I talk with would be novelists who don’t actually write anything.  They tell me all about the world, the characters, the concepts, but on paper they have nothing more than a few notes.  Not one word of dialogue, action, nothing.
4. Keep writing your story.  Yep, keep at it.  Sure you may take a break now and again to go through your notes and revise your ideas, but KEEP WRITING THE STORY.  Otherwise you’ll just end up with a pile of notes.
5. Finish the story.  It may sound a bit strange but it can be hard to just call the story done.  Figure out where the climax is, tie up the loose ends that actually need tying up and finish it.  Call it good.  We don’t need to read about the hero’s sixteen grand children and their battles with the Dragons of Orgnark.  Save that for another novel.  Finish this one.
6. Go back a re-write your story.  You thought you were done didn’t you.  Go back and cut out half of everything you have written.  Hack it.  Slash it.  Get mean with that red pen.  Then re-work it again.  Go through the whole book, sentence by sentence and word by word.
7. Take a break.  Now is a good time to get away from it.  Let your girlfriend read it.  If you don’t have a girlfriend then now would be a good time to get one.  Let it sit.  Let it stew.  Let people whose opinion is worth anything take a look at it and then listen to them.
8. Revisit step 6.  Be sure you have taken at least a couple of weeks off.  Then go back and do step 6 all over again.
9. Repeat steps 6 through 8 a couple of more times.
10. Call it good.  No it isn’t perfect.  It isn’t the greatest thing you have ever done.  You are still unhappy with it.  You are still disappointed.  You still want more.  Too bad.  It is done.  You are finished with it.  Accept that and go on to write the next novel.

If you were expecting something more directly fantasy related – tough.  A story is a story is a story.  The setting is less important than the story.  If you haven’t figured out how to write a story then you should quit now.  Learning how to write a fantasy novel is no different than learning to write any other story.  Odds are that if you want to write a fantasy novel then you already understand how fantasy novels work and have a good idea of what to put into your world and charaters.  The rest is just writing a good story.