Here's what I found helps to start with but I don't know your genre. Mine is anything in the thriller, or sub genres and at the moment l'm writing a suspense thriller series as a disaster story.
Obviously, before anything, there has to be a kernal of an idea for the story, the bigger the idea the better, but you should not even start if you don't know its intended genre. In my case, I looked up the suspense genre and the consensus was that opening chapters are more about introducing the characters than an inciting incident you would find in say a crime thriller, but with maybe a little foreshadowing of what might come and the suspense builds from there. Whatever, searching the Internet will come up with the expectations for your genre.
This is exactly true of blurbs and again you can search your genre on the Internet for examples. In my case in simple terms it's, who it is and what they want. What or who stands in their way, and finally what are the stakes if they fail. So now I can start with a blurb and I've just done this off the top of my head as if I was planning to outline a story.
All Jack wants is an uncomplicated life. When a body is found in his back garden, he becomes the main suspect. Someone out there wants to destroy his peaceful and quiet life. Jack will have to break free of his acceptance of the norm if he is to discover who is trying to destroy him and bring the killer to justice. But then things take a turn, when a relative is murdered, further implicating him and he receives a warning of further deaths unless he confesses to the murders. He is running out of time and options. If he fails to discover the killer, at best he'll spend his life in prison and at worst more people he loves will die.
Knowing this and that the blurb has legs for the genre you can move on. All stories start at A, then work there way to Z at the end. The blurb doesn't give this away, but you really need to know it as everything in the story drives to that end. . The trick is to get from A to Z in logical steps that will satisfy reader expectations.
Here is where the three act method helps, and again, if you are not familiar with it, look it up on the net. Besides having logical steps, you can determine the pacing of the story.
Yes, you can do this in your head, and decide as you go along where to introduce say a detective or his attorney, maybe give him a wife and family or a love interest and any number of red herrings. But then you have to ask yourself when do you introduce them and for what purpose. How are they motivated as it relates to the stoty. If you are aware of the three act structure, then you can decide how many chapters to allot to each act. So far you haven't needed to outline, as you are more at the brainstorming stage, but you know your basic story from the blurb.
You can make outlining as simple or as complicated as you want.
You might want to start with the setting and write out the world where it is set. Again this can be as simple or as complicated as you have in mind. You might want to make up your own political system, economy, and map of the area, or if it exists to search for an area map and copy and paste that into your outline for say references of distances between towns or whatever.
It may require research on say scientific stuff or crime procedures, radio call signs, or whatever. Copy the links and paste them into your outline for easy reference.
Move onto character outlines, give them a background and character traits and how one will relate to the other. Also character arcs. Will they stay the same throughout, how do you expect them to change. If you don't have all the characters to start with, you can add to them later. You might even benefit for giving the town and townsfolk where it is set a character of its own.
Now you can really start on the story by brainstorming, or as I call it daydreaming the story with a notepad to hand. In essence this is the pansting stage. Then transfer this to your chapter outline in note form. I doubt anyone can simply imagine the whole story chapter by chapter in one go. Write out your list of chapters, 1,2,3 etc, and give yourself and average word count per chapter to reach a target word count for the story.
Decide where you want each act to fall in relation to your chapters and mark it to give you a sense of purpose as to what is required upto or from that point. Now imagine each act in relation to how the story and characters will develop to a conclusion with rising and falling action. Once the story is in your head, take it an act at a time and start putting notes at each chapter for what you want to achieve. Then repeat with the second and third acts and you have it outlined. There should be no writer's block from there, that comes at brainstorming, daydreaming, pantsting stage and will determine if you will ever complete the story. If you can't pants the outline in note form, you won't have much joy pantstng the full story.
The chapter outline is what James Patterson uses to give to his Co writers and their imagination a prowess as a wordsmith do the rest.
