With a sense of your purpose for writing, your audience, and how your writing will be published, you now need to figure out what your project needs before you can start. This might mean conducting research or planning back story, or it could mean reviewing things you’ve written in the past to figure out what you have and what you need. Your plan is your roadmap. It gives you a clear sense of where to start and where you should end up.

Planning for Nonfiction Authors

Lastly, you have to figure out what your project needs and actually lay out the plan. Once again, I recommend looking at what those you admire have done and taking notes. As you assess what’s out there, you’ll get ideas. If you’re writing technical nonfiction, I suggest the following prewriting steps:

An absolute must-have for anyone hoping to publish their writing.

Determine your book’s mission; summarize what the book will do in a sentence or two. Include who your target audience is. Ex: This book will give beginner novelists the knowledge, resources, and tools they need to complete their first novel, to edit it, and to market it.
Decide on your story’s contents. Aside from a preface / intro, conclusion, etc. what chapters will your book need to satisfy your audience’s needs? A lot of writers make the mistake of editorializing to the point of turning off their authors. Remember why your audience is there. Ask what they need to know in order to have accomplished whatever it is your book promises.
Writing out the chapter titles will give you a good sense of the book’s structure. You can change the names, add, reorganize, etc. later or in revision; however, you have to have a starting point, right?

A great resource if you're planning to write nonfiction is William Zinsser's timeless On Writing Well: A Classic Guide to Writing Nonfiction.

Whether you're a plotter or a pantser, Stephen King's memoir and writing advice is straightforward and is the kick in the pants you need to elevate your writing game.

Planning a Novel for Pantsers

Some of these tips apply to creative writers as well—whether you’re a plotter or a pantser. Here’s my approach to both:

With the short story I wrote recently, I had a main character. Because it was a travel story, I knew my setting was important to the story. I also wanted to incorporate the real ghost story into the otherwise fictional piece. Beyond that, I wanted to write something spooky.
My better ideas came in revision because I asked myself smarter questions. Who was my protagonist? Did I want people to like her or not? Did I want to like her? Did I like her? How does she change in the story? Does she change? What is the story’s antagonist? What happens in the story? What are the major events at the end of acts I, II, and III?
Since it was a short story, I didn’t mind pantsing and doing a full rewrite once I had a clearer vision of the story. (This is not something that I enjoy doing with a full-length novel that I wrote because I zero in on what’s not working versus what’s great. Stephen King, on the other hand, loves revision and looking at his first drafts.)
After the story was rewritten, I was able to go back in and flesh out the moments that needed more meat and to cut the moments that didn’t advance the plot. In On Writing: A Memoir of the Craft, Stephen King recommends, and I concur, that in revision, you should cut 10% of the original writing. Leaner is meaner (this is true for nonfiction writers as well).

I liken this approach to painting when you start with a sketch, then you go over it with the underpainting, then you add your first layer of paint and you continue layering until you’re satisfied with how the work looks. Next you start adding shading and highlights to give the image dimension and texture. The same is true in writing. If all you do is an underpainting, then don’t be surprised when the response is underwhelming.

Planning a Novel for Plotters

When I plan a story, here’s how I go about this and recommend doing so for other novelists:

Figure out who your characters are. What are their backgrounds? Their motives? Who hurt them? What do they love most? The more you know about the characters, the better your story will be.
Write out the scenes you already know. When I come up with an idea for a novel, it usually starts as a ‘what if’ question (like a loose sketch) and then I start to envision scenes. I write them out. Usually this happens before I really know the characters, so the scenes will usually change a lot…especially as I get to know the characters.
Next I string the scenes together and figure out where the blanks are. Sometimes, I let those blanks get filled in while I’m writing (this is good if you’re a plotter and a pantster). Sometimes, I fill in the blanks in fairly good detail.
Figure out what your pivotal scene is. This is sound advice passed down from other writers that I agree with. When you know what that scene that makes you lose your breath looks like, you can build around it.
Understand what your story’s about (if you can). Sometimes, this doesn’t come until the end (like with my ghost story); however, if I go with a more involved planning approach, I usually have an idea as to what the story’s about, and I have fun getting a sense of how the finished product will look before I write the first word. It’s really inspiring. Just as pantsers are excited by what happens next, when I plot, I’m excited to see exactly how it will all unfold because even though I’ve planned my story, I still don’t know just how it’s going to play out.

You’ll know when you’re ready to start writing. It’s like planning a vacation, to throw in another metaphor. You’ll know when your bags are packed, the car is gassed up, and your GPS is set. You might hit some hiccups in your travels, but that’s okay. You can practically see your destination because it’s so well planned.

Importantly, ever writer and editor has a different “how to” approach. These are what works for me and are what I find works for a lot of people; however, Kurt Vonnegut who liked to write and rewrite each page until it was perfect would’ve scoffed at this method. What I’m saying is that every writer is different. There’s not perfect how-to guide. You need to experiment. Find what works for you. The only way to do that is to write. Write often. Write what you love. Write like it’s your job. Write like your life depends on it. That, I can say with a fair amount of confidence, is something that most writers, regardless of how they approach writing, can agree on.

Even with great tips, writing a novel or a book is easier said than done. If you’re one of those writers who knows that if you can just write that first book…just get a publishers…if you can just, then you’d be making it, but you don’t know how to get started or to finish your writing, consider working with a writing coach. A writing coach is like a personal trainer but for your writing. A writing coach will have you reaching goals, flexing literary muscles, and squatting published manuscripts in no time.