...Listen to Nike on this one, and simply do it. You’ll never finish it if you never start. That’s what has helped me- just beginning, getting something down. Then you can always add to it.
The best way to get started, in my opinion, is to watch yourself- when you have one of those thoughts that make you go, “Wow. That’s really interesting” stop for a moment, and write it down. I personally often hear conversations between characters in my head, and if I have the time, I just sit down and type it all out until the inspiration runs dry.
Then you have something to work with. Reread over what you wrote before, and add to it. Run it over in your head. Try to figure out the rest of it. Start with a scene, a conversation, a character, a conflict, a setting, a time, anything, and build up from there.
Anyone can write a novel. Make an effort, and be one of the few who actually DO.