I usually have a couple documents going for a story at once, one that is the actual document of the story and one that is the "Notes" document. And the notes document is typically a huge mess. It has partially written scenes in it that I needed to throw somewhere as I came up with them, it has a "brain dump" of everything that has to happen in the story and it's usually just me typing in a ramble. The story I just wrote has a big twist halfway through, and I have a bullet list in that notes document called "Before the twist!" of all the things I needed to make sure I included in the first half of that story.
I don't really outline by the chapter (the only exception is Running Up That Hill because certain things have to happen on certain days because that's where they happened in real life) but I definitely make sure I have a clear direction of where the story is starting, going and ending. I find that when I start a story without knowing those things, I fall off right away. There are things that change along the way, of course, but the main points always stay the same.
As for first person vs third person, it's funny. In BSB fandom I will typically write one-shots in first person without even giving it a second thought. But usually when writing something longer I stick with third person.
I don't know how slash writers write in third person LOL. I'm thinking slash, for me, will always be done in first.
This amused me, Julie, because my prime reason for writing in third person now is because I don't think I could ever write a slash in the first person! The male pronouns are definitely a pain, though.