When I get started on an idea, I do like to write my initial thoughts, or lists, by hand, on paper. Only later does the idea get transfered to the computer. However, computers have made the whole process much easier, because there was a time when I used a typewriter, and more than once wanted to throw the stupid thing out the window, and would have, if hand-writing hadn't been so tedious.
Nowadays, I tend to need that kind of ultimate quiet you only get late at night. There is something about darkness, solitude, and the knowledge that there is no one out there who is likely to bother you, call you, email you (unless you have friends in a different time zone, that is) or in any way break into that bubble, that zone of thought that I need to create. This changes when I am deep in the middle of the work, or in that "flow" that makes it possible for me to ignore all outside distractions. But when the work is beginning, or is nascent, those distractions are really annoying, and tend to prevent me from getting any work done at all.
But the most important thing I usually need to do before I can write is research. I am more of a researcher than I am a writer at times. Without research, I don't feel comfortable writing much of anything, I'm afraid. But then, I write historical fiction and academic-type stuff, so research is crucial for me.