Because duh, how can you write a novel if you don't even know how a novel works? If you've got a particular genre in mind for writing, you can focus in on that for your reading, but all kinds of books can give you inspiration and knowledge. This advice has been given by every successful novelist ever, so I suggest you use it. You can also spend time on movies and TV shows to follow the storytelling there. You can learn from everything!
For pantsers and planners alike, I think the most important thing is to start off knowing what your climax is going to be. I figured this out after I wrote THE PSYCHIC STORY, because I then had to rewrite the climax of three times. Keeping that ultimate moment in mind will really guide you, especially if you start running into roadblocks or losing steam.
It doesn't just happen magically. Novel writing takes real work, effort, and time. So get ready for the potential time crunch. If this is what you really want, then you have to give some things up. Also, while you're writing, you have to actually write. It doesn't get done on its own. Don't procrastinate, or you'll never get anywhere. Stay focused, and put that butt in that chair.
It does take practice to get to a full-length novel. I wrote a lot of poetry, a bunch of diaries, and at least three novel attempts before I managed a complete, full-length novel. So don't be disappointed if you don't manage it at first. This is an acquired skill, and you will always be learning new things. You just have to keep trying, which is my cardinal rule for all things novel.
If you've written a novel, how was the experience for you?
Images via myparkingsign.com and money.bhaskar.com.