Decide what you want to write about. Then write the story only you can write.
If you're unsure of the story, just begin writing. The story will come.
At least that's been my experience, although I admit, it's probably not the most efficient way.
If you can find another story-teller and read each other's work, and comment honestly, that will help a great deal. But recognize that most people you ask to read your story will not be completely honest with you - they don't want to either spoil the friendship or spoil your enthusiasm.
Ask yourself what you want. Why are you writing novels? Is it for self-expression and fun, or is it because you want to sell a lot of books. If it's the second, then think hard before you start - make sure that people will want to buy what you write - that's why there are so many romantic novels around :) Selling books is highly competitive, so if that's what you really, really want to do, do your market research.
