"...for bigger fictions (maybe 10-20 chapters, or more) for a big fan fiction or OC fiction, how much do you plan out? Since you are an actual Author I was just wondering how you would fair on this idea?"
How much do I plan out for one of my novels...?
-- I detail everything. Seriously.
I start with a basic plot formula and extrapolate on certain points as needed.
-- Romance needs extra doses of lover's angst, Gothics need psychological breakdowns, Horrors need room for monster attacks, Sci-Fi's and Fantasies need moments of wonder... This gives me a rough plot outline to work from.
Next, I break down each of the Three Main Characters: Hero/Ally/Villain.
-- This is to make sure that they are 'psychologically' in sync with the Plot and Each Other, so their actions/reactions will mesh in the way I intend. (Ahem... That their personalities will clash nicely.)
If I'm doing a Historical, I also look up the 4 years they were in High School (at ages: 15, 16, 17, 18) and check out what books, songs, movies, and/or TV shows were popular during that time. Believe it or not, those are the most common foundational points in most people's personality.
Think I'm kidding? Look up your own high school years and check out what books, TV shows, songs and Movies were out during that time. Now consider how much those things STILL influence you today? (If you're still in school, check out your Mom's or your Dad's high school years. The results will be shocking!)
Once I get my main characters down, I sketch out the major support characters.
-- I don't go into detail on them. Just names, jobs, physical descriptions, and what I've based their personality on, (Scorpio and an INTJ?) or who. (Riddick under a new name?)
Why not detail the Support characters?
-- Because I don't want to find myself attached to a character that ISN'T who the story is about.
Then, I map out the LOCATIONS I intend to use.
-- Location Research is especially important if I'm writing a Historical piece.
I begin by researching the NEWS local to that area. Did riots break out the summer my story happens? Was there a killing snowstorm that winter? Droughts? Floods? Fires, Quakes...? Weather and social conditions are vitally important because these conditions will make or break all the plot points caused by Setting.
In other words, if one location won't work-- "Oops, on that day, there's a riot on that street..." --I'll have to thrash out either a way around it or find a whole new location -- or a new Time Period.
Case in point, I seriously thought about writing a Meiji Era story--until I discovered that Japan was in and out of war with Russia and China that whole period because of WWI, plus a few other less than savory--and still hotly debated--skirmishes in Korea. Then there was the Kanto Earthquake and hundreds of massive city-wide fires. Also, their Justice system was NOT Just. (If you had money you were innocent. If you didn't...you weren't.) In short, it was waaaaaaaaay, too much work to thread my little story in the middle of that mess.
- If I'm using a completely fabricated world or country, I suss out the political system and history for that country or set of countries for that last 200 years--or more. Then there's the time system: how many hours in a day, days in a week, a month... (Is there a moon on this planet--or two?) How long is a year? Education system, medical system, money system, invention or magic system, what occupations are available...etc.
- If I'm doing a Sci-Fi or Steam Punk, next is Invention and Science research. It always pays to know what actually existed during a certain time period and what current science says is possible in the future! I normally find major inspiration during these research sessions.
- If I'm doing a Paranormal or Fantasy story, Mythology, Magic and Paranormal research is next. Since I've got quite a home library on these subjects, this is just a matter of pulling a book from a shelf.
I believe in a Total Immersion style of writing. In other words, I want to know the world so well I can simply step into the mind and skin of my main character and LIVE the story.
In the course of writing, some plot points will work and some won't. Some locations won't offer quite the right atmosphere I intended for a scene. Sometimes a whole new character will step onstage and become the Ally to the main character or the Villain INSTEAD of the one I mapped out.
When that happens, I take a few moments to extrapolate how such changes will affect the story. If the ending doesn't change--or a better one suddenly crops up, I go with it. I DON'T stick that hard to the plot outline. I change as needed to make the STORY better--not my ego, or worse, my Character's ego.
And...that's pretty much it. *Grin*