If you want to write novels, then treat it like it is a job. You have to write and get your word count in.
Now to write a novel, it comes from a single idea. I usually start my ideas from a single image or a ‘what if’ question. ‘What if you were vacationing in Tokyo when a society collapsing event took place.’ Or an image of a really cool character. Author Brandon Sanderson wanted to write a story about a guy with a magical beater sword. He wrote his Stormlight Saga Novels from that single thought.
First. Find that really cool idea. Don’t worry about where you are inspired from. Don’t worry if it has been done to death.
Second. Start to ask questions about that idea. Who, what, where, when, why and how. Create your characters, create a conflict. Create a world if necessary. If you need to, write it down. I do recommend writing it down at some point before you forget details. This is where you take that blah idea that has been done before and turn it into something of your own.
Third. Step two takes time. You may find that the idea is hogwash and full of holes. If so, file away and move on. I have about a new idea a week. Most never get written down as they are bad. But once every few months, I have a grand idea that is beautiful. It gets written down and filed for later use. (I have three projects on the go at some point of completion with about a dozen ideas in note books for later use. Kinda like Skyrim Quests.)
Fourth. Plot out your novel. If you are an outliner, outline. Or whatever. Plan the novel. Where is it going? How are you going to get the character from point A to B? What are some of the trials and tribulations that he must overcome? Even discovery writers do this.
Five. Write. Every day. NaNoWriMo style. Go to http://writetrack.davidsgale.com/pls/apex/f?p=228:LOGIN:::::: It is a free tracking site that gives you that chart like NaNoWriMo. I don’t think that it is supported anymore, but I can’t find one that is. I use it though.
Six. (Should be done throughout in my opinion, but whatever) Read. Study. Read books on writing. Read fiction. Listen to podcasts about writing. Watch webinars.
Write like it is not only a job, but a way of life. Getting good at writing isn’t about writing one novel. It is about the process. It is about writing the novel. Polishing the novel. And completing the novel. Over and over again.
A painter didn’t paint one painting and have it a masterpiece. neither do novelists. Write lots. Write many books. And don’t obsess over the one. Learn when it is good enough. Learn when to stick it in a trunk and to walk away.
David Eddings once said to become a writer you must write a million words. Then to burn them. Then you can be a writer.
In conclusion to my rant, plan your book. You can’t just pick it up cold you have to plan it.