I am a writer, I tend to write and then write my outline. I have done this for many years with papers and stories but it doesn't seem to work with my books. Is that a good strategy?
I do a somewhat similar thing, and it certainly can work. Hopefully my methods will help you come up with your own system.
I have many ideas all of the time for interesting scenarios, relationships, scenes, conversations, even philosophical outlooks on life that characters may have.
I then write them down on some paper, and stick them into a (currently very disorganized) folder. I then usually forget about them for a while.
Occasionally I will get a good idea for a story. I file those separately. Currently I have about a dozen story ideas. I have no idea what will happen in these stories, some of them just have a premise, others have just a beginning, or just an ending.
Every now and then I will go through my ideas folder, see what things I wrote down, and some of them will fit perfectly into a story idea, so I take it out and file it with the story it will fit with.
The story I'm currently writing I have only planned around 95%. I know the majority of what will happen in my story, but there are still chapters that are unfinished. I started writing it when it was around 90% planned out, and as I have gone along some of my previous ideas have fit into the empty spaces.
This method has some drawbacks. I haven't yet reached a point in writing my current story that I have completely unplanned, as I usually think of something or find an idea for it before I reach that point. However, if I do reach an unplanned point I will either have to stop writing, or skip that chapter and move onto the next one, neither of which I think is a good idea.
In addition, it requires me to be very flexible, and absolutely ruthless. I have had to edit parts of my earlier chapters multiple times in order to make it fit with later character development etc. There have been parts that I have needed to remove entirely because they no longer fit with my constantly evolving story.
This can be very time consuming, and sometimes I struggle to find the motivation to write some of the weaker parts of my book, as I am worried that I may come up with a better idea later and I will need to rip it all out again and rethink what I've just written.
In addition, I have a dozen unfinished stories that I may never find a way to complete, which is no good to anyone.
However, this method has its advantages too. If I only started my book when it was 100% thought out and planned, I still wouldn't have started it, so it allows me to think up new great ideas whilst still in the process of writing, as my story is not so rigid that I can't put extra things into it.
I have found that this makes my story flow better, and have a more natural evolution as I am discovering the next part of my story alongside my characters, so there are no parts that do not fit together neatly.
As for my other stories; on at least one occasion, I have looked at a single idea, and with this one small addition to a story, I managed to combine two of my story ideas and adapt them into a single idea for a book. Had I tried to wait until I had a full plot in mind before writing a story, I would have a quarter of two future books as opposed to around three quarters of the plot finished for one future book.
In summary, in order for this to work you need to be prepared that some of your best ideas may never get used in a finished story, as the last thing you want to do is to shoehorn something into a book where it doesn't fit.
You also need to be patient. Your story will take a long time to complete with this method, but I feel that with mine it is constantly improving, and am willing to spend the time to end up with the best work that I can possibly do.
Hope this helps!
What you are describing is being a discovery writer, also called a pantser (as in "by the seat of your pants").
The purpose of an outline is to establish a coherent linear structure for your story, so all the plotlines work all the way through. If you just write your entire story first, and then reverse-engineer it to fit an outline, you can make it work, but as Mike Ford notes, you must be absolutely ruthless about it.
Generally speaking, if you are writing a relatively standard, linear narrative, an outline is a good thing. Whether you write the outline first and base the story off that or write the story first and then hang the bits on the outline until it works is entirely a question of what you are comfortable with as a writer.
What I don't think you can expect is to have a coherently, fully-formed novel leap from your fingertips in the first draft without having some kind of outline, structure, or plan set up beforehand (whether you write it down or not). Part of the point of discovery writing is that you, quite literally, don't know what's going to happen next. This is the opposite of an outline, where you have already decided what's going to happen next.
Your question should not be "Is this a good strategy?" but rather "Is this a good workflow for me as a writer?"
There are two ways to write a book:
a) Have a definite plot / story in mind with characters.
b) Start with some scene and build up the story as you go along.
In the second method, you might risk losing track of your story's logical continuity link.
I'd say it's better you have some plot in mind and develop it fully into a story.
I tend to write my stories "backward." In a 12-chapter novel, I once wrote the first three chapters, then Chapter 12, Chapter 11, Chapter 10, Chapter 9, then chapters 4-8 in some random order.
I know how the stories begin, and how I want them to end. The "middle" chapters are the hardest for me to write, because I'm not sure how to get from A to B. So I let A (the beginning) and B (the end) expand, until there is little enough left in the middle that I can force it to fit both ends.
My secret is to have solid foundation (beginning). Then when you start at the end, you have something to "back into." Otherwise, you don't.