A: I tend to write in a pretty linear fashion -- start at chapter one and keep going. Sometimes I have an inspiration for a scene pretty far ahead -- or even the ending -- and I'll write it down and file it away till time to use it.
I edit as I go -- reading what I wrote the day before and fixing what needs fixing before beginning the next bit. This has the virtue of getting me well back int the story before I write something new.
If, as sometimes happens, events prevent me from writing for a week or more, I may go back and skim through everything before continuing on. And I always make some changes. But I try to keep moving forward.
If I'm stuck or out of steam for the main story, I can always go to the secondary, historical subplot -- which also proceeds along in a linear motion. Here too, I read and edit the previous work in this story before laying down new stuff.
Some people swear by writing a first extremely rough draft very, very quickly and only after reaching the end do they go back and flesh it out with description and such. It sounds good but I don't think it would work for me as my ideas are developed at a leisurely pace. I may be fifty pages from the end and still not be sure who the villain is.
A: Around 1,500 words or around five pages (double-spaced, of course) is what I shoot for. That's about half a chapter -- at least in the first two-thirds of the book (the chapters get shorter toward the end in an attempt at picking up the pace.) And it's pretty polished.
Sometimes I do better than this; I have done 5 thousand words in a day (once or twice) -- sometimes it's a struggle to get 200 words down. The muse is fickle.
And sometimes there are days when Life interferes with my plans for writing. Stephen King famously writes every day of the year. I can't even imagine that kind of dedication. But then, I'm not Stephen King.