Study recent issues of Publisher's Weekly magazine to get an idea of trends in book publishing. It may be easier to get your book published and sell many copies if it fits within a current trend.
Create an outline of the novel you want to write. Include details about the three most important elements of a story: your characters, setting and plot. Your plot should include a conflict and resolution.
Write a first draft of your novel before doing any editing. It is more important to get the ideas written down before pursuing perfection. If you experience writer's block, skip ahead to write a different part of the story. There is no reason the story has to be written from beginning to end; it just has to be arranged that way when it is complete.
Read your first draft or ask a trusted adviser to read it. Read it aloud to notice where the language doesn't flow smoothly. Mark the places in the story where characters or plot twists don't work well. Write a final draft, incorporating these changes.
Send a sample chapter of your manuscript, along with a cover letter detailing what the story is about and what other work you have written, to a literary agent. A literary agent can make it easier to get a publishing house interested in buying your manuscript to publish your novel, and can negotiate better terms.