Sarah Salway offers a lot of answers to the question, 'How do you start a novel?'
Since so many students have written stories, I'm going to do an exercise in which we take a short story and do as Julianna Baggott suggests here, "open up the pleats."
If you've got stories or one story that resonates with you and readers, you can take that story and look for pleats -- ways to open it up. There are natural constraints on stories -- size of the cast of characters, point of view (one incident -- four points of view? maybe a novel), time, geography, insight, back story. If you open one of these elements in a story, you might have a novel.
I'm going to use a very short story--well, it's actually a poem. Robert Hass' "A Story About the Body." The story is an incredible example of compression; what happens when you open up the potential pleats? Dramatize the days in which the composer and painter get to know each other and become attracted to one another? Incorporate the composer's backstory? Include the Japanese painter's point of view? What about her backstory? What if she lost her husband because he couldn't cope with her mastectomy? And she came to the artist's colony to recover, only to be rejected again by a young composer who rejects her? And is the bowl the end of the story? What if it's the hook, the last thing that happens in chapter 1? What could happen next?