1. Read everything you can get your hands on. Decide what genre you enjoy reading the most. Study that genre. Learn from the masters.
2. Buy a notebook or a computer and start writing every day. Think about the genre you enjoy reading and dream up a story. Sounds easier than it is. For me it all started after reading an article about Diamonds. I started jotting down notes in a notebook at lunchtime away from my day job. Soon I had what I thought at the time would be a great thriller novel. It took me a year and a half to write and rewrite the story several times. Eventually I put this first novel aside in a desk drawer and started a second novel with an entirely new cast of characters.
3. Join a writing organization like Mystery Writers of America, Romance Writers of America, Thriller Writers International, or a genre specific group. If you have the time and the money attend a writers conference. I went to my first, Killer Nashville, in August of 2012. It was a great experience and I got to eat dinner, and talk to published authors. One of the highlights was talking to members of the FBI, Tennessee Bureau of Investigation, and local police. I remember how inspired I was with my writing after returning to my home. Writing Conferences range from big to small.
4. Research every part of your idea. This includes building a character sketch for each of your main characters and asking yourself their likes, their wants, their dreams, and anything else you can think of. There are several good character sketch questionnaires on the Internet. The next step is to think through any action scenes you intend to write to ensure that the cinema-graphic details of the scene are correct. Research anything technical or detailed in the novel. Identify the motivation of each and every character with the story.
5. Outline each of your scenes and chapters. There are two types of writers - organic and outliners. I've heard about many writers who just free write 500 pages and have a first draft. If this works for you do it. If not construct an outline. Another thing to remember is to not box yourself in with the outline. It's just a guide to help you plot out your novel. It becomes valuable with each new draft and can help you keep everything organized. There are many software tools such as Scrivener that help you outline.
6. Write your novel. Read it cover to cover. Congratulate yourself for accomplishing a task that many set out upon and few conquer. Everyone wants to write a book. You've done it. Now the hard part begins.
7. Rewrite your novel.
8. Set it aside for a month. I've heard this advice from many, but the one author who explains it the best is Stephen King in his book "On Writing". This is a good time to start learning everything you can about the publishing industry.
9. Edit your novel. Rewrite it. Edit it. Rewrite it. If you feel like something is wrong with the novel something probably is. Print out your novel, read it, and edit it on the hard copy. Read it out loud to yourself. This is especially helpful when something doesn't seem right, but you can't put your finger on it.
If you have the money you might consider hiring a freelance editor at this point. New writers often discover that their story is not as good as they thought. Editors can help with what's called developmental editing. Once the story is set they can help with line editing and copy editing.
10. Beta Readers - Put together four our five pages of tough questions about your novel. Find 5 beta readers who regularly read in the genre you have written. Give them the questions and a hard copy. I used Kinko's to print out hard copies until I decided to buy a black and white laser printer. In the long run the printer was much less expensive than having books printed at Kinko's. Find beta readers who will be honest and critical of your work. This is what you want and need at this point.
11. Rewrite, edit, rewrite. Look at grammar, sentence structure, and cut anything that doesn't move the story forward.
12. Write a Query Letter. Good luck with this. It can be tough to do at first, but there lots of great resources on the Internet to help.
13. Research agents on query tracker and agent query.
14. Send out Query Letters.
16. Land a literary agent.
17. Sell your book to a publisher.
18. Rinse your hands and repeat.
Good luck fellow writers.