Writing isn’t just about sitting down in front of your chosen writing software and typing away. Or at least, it shouldn’t be. Nearly all writing should begin with some organization. What are you writing about? Is it fiction, non-fiction, academic? Something else? How long is it Does it require research? Will it have a lot of characters or minute plot points that need keeping straight? If it is more than a couple of pages, laying out things in a logical manner will help you greatly.
There are many supplemental tools for helping with this. What you use depends upon what you are doing.
Take academic writing, for example. There are at minimum two tools you should be using: an outline and an annotated bibliography. An outline helps you to get all your thoughts together, setting order to your paper. You can start off with just a little, filling in as you go. What is your argument and thesis statement, or needed background; why are you tackling this specific topic? Do you have a book review or author bio due, or a literary review or methodology required? You certainly must lay out the evidence for your argument, plus your conclusion. The fact is, in theory you can fill in so much in the outline that the paper is done before you even begin writing it as such. The paper will be all the more cohesive for it, and will almost certainly require less editing than just typing from scratch.
As for the annotated bibliography, it is of tremendous help even if not required by the professor. You can always delete it later. But all papers other than simple essays require bibliographies, and you can have that biblio done and ready before writing. The annotated part helps you know what book is being used for what information found on what page, and in what part(s) of your paper. You can refer back to it when creating your outline and/or paper. Then remove the annotation later, post final proofreading. Other tools can include online citation generators (make sure it matches your required style guide, and understand even then most of these generators can make formatting mistakes). For academic work, I personally also use a separate work doc. I have the annotated biblio laid out by book, but the other work doc lays the same info out by type of information. What sources are being used where in the paper? I can easily cross-reference, and it helps even more when laying out the outline and writing the paper.
What about fiction manuscript writing? What tools are available? Here, your best friend is a spreadsheet. In my work, I’ve seen too many clients who either dispensed with this, or never thought of it in the first place. This is helpful even if the work is non-fiction. But for fiction, it will be detrimental to your story to not use one. Every character can be laid out. What is their name? Their function in the story. Their age? Height, weight, hair color, eyes? Background? Inter-character relationships? Anything that might be mentioned in the book, so that you avoid contradicting yourself, with your blonde, blue-eyed heroine later becoming a green-eyed brunette. Oops! Or Bill’s girlfriend later being called Nathan’s girlfriend. Double oops! The spreadsheet can include characters, locations, animals, even plot points, though you may choose to keep a separate word doc for plot. Outlines can be useful too, though I never use them in my own fictional work. [They are more helpful in non-fictional writing, under the same principle as academic work.] Personally, I almost always write out a summary of my proposed story. As though the work has been completed and I’m just summarizing for someone else. Nothing says that you can’t change the story as need dictates. The point is to have an idea where you are going. It is the equivalent of going on a driving trip, having mapped out your way, but willing to change it if a detour is needed. Rather than, say, hitting the road without a clue where you’re going.
It does require patience to use such supplemental tools. If you are starting and have an idea where you are going with your thoughts, you want to begin writing immediately. But you will be far more likely to fall victim to content errors, and plot confusion by doing it that way. I’ve seen it happen too many times. Better to deliberately lay it all out, and proceed accordingly. That can only be done by using other tools, even if it’s just a legal pad to jot things down on.