Devise a plan. You need to think about what you will write and when you will write before you even start. Try to find time to write each day preferably the same time each day so writing becomes part of your routine.
Write a bit each day even if it's just your ideas. You can sketch your plot, write about your characters and describe your scenery. You need to know everything about your characters' personalities even if you aren't sure how the story will turn out.
Finish all the chapters of your novel and then put the book aside for awhile. You want to remove yourself from the story so you can look at it with fresh eyes.
Edit your chapters for style, content and plot. Make sure the story makes sense in the order you have it and that your names and places remain consistent. You may need to make several edits to your novel.
Ask someone to read the story for you to see if the book makes sense. You don't want any confusion or inconsistencies in your novel. Fix any problems.
Create a detailed chapter by chapter outline of your story and write a one page synopsis of the whole novel. Publishers will look at the outline and the synopsis to decide if they want to read your novel.
Buy a writers' marketing book like the Writer's Market so you can find a place to sell your book. Market books give you names, addresses, websites, emails and telephone numbers for publishers.
Skim the marketing book to see which publishers want the kinds of novels you write. Follow the publisher's guidelines regarding what to send to the publisher.
Write a cover letter for your novel explaining what you have written, why you wrote it and why the book will sell well. You need to know all of these answers before you send your book.
Put your outline, synopsis and cover letter into an envelope and send the book to a publisher. Make sure you address it to a specific person.