A: Probably the most oft quoted piece of advice is "write what you know." I'd revise that to say "write what interests you." You don't need to know a great deal about a subject at the outset--I wrote a novel set partly in a Federal Reserve Bank and had never set foot in one--but interest in the subject is a way of signaling to oneself that you want to learn about it, and I think the curiosity behind learning and writing are not dissimilar. Thus, as far as subject matter goes, I could refine my answer to say, write about what you want to learn about.
As for the practice itself, writing prose takes time. Keeping a regular schedule is vital, in my experience. There is so much failure built into writing--so many drafts of things you'll never end up using or will use only a sentence of--that you have to be willing to spend a good deal of time working even if there is no satisfying ratio between the time spent and the finished pages won. So I would be determined, I would turn off the internet, turn off your phone, and write however many hours a day you can manage. We live in a wildly distracted age. In order to hear the voices inside myself that want expression, I find I have to try to quiet or even silence the louder more common ones of everyday modern life.
A: I think this varies widely by the subject matter and the author in question. As a fiction writer, I research as much as I need to make a scene or character plausible and convincing, but not more than that. I'm not trying to provide an authoritative, non-fiction account of anything. My time is mostly spent trying to find the rhythm of the prose that best fits the character or story. That, in a sense, is my main research. If I need facts, I will go and get them. And obviously, as I said in my previous answer, if I'm writing about something that I know little about, I will read background material and immerse myself in it for a while, but that isn't usually how I start.
A: I began with a scene I knew I had to write: a scene at the end of the book between the elder brother, Michael, and the younger brother, Alec. I didn't know at the outset if this would be a short story, a novella, or a full novel. I just knew I had to write that scene. So the question then became what would lead up to it? How would the reader learn the full import of what was taking place during that scene?
The next thing that came to me was the vision of the mother driving with her family, her husband and young kids up to Maine for a summer vacation, and at that point I realized I had the books ends, as it were, of a novel. I would tell the whole story, from the kids being young to how the brothers, in their mid to late thirties wound up back in the same cabin in far more dire circumstances. From there my challenge was to find the right voice for each character and piece together the story from the five different points of view it is told in.