In an example of synchronicity, articles about first drafts hit both 43 Folders and MacDevCenter today. 43 Folders suggests Just Doing It, while MacDevCenter explores tools (some of which don’t exist yet) to help eliminate distractions so you can focus on writing (instead of editing).
If you read the comments in the MacDevCenter article, you’ll see where I suggest the hoary Unix line editor, ed, for first drafts. It has been part of Unix systems since the first version in 1970 and is still lurking at the bottom of the most modern version of Unix (aka MacOS X). There’s also a neat trick for disabling the GUI at login time, leaving your entire screen dedicated to a white on black console screen: type >console instead of your user name and hit Return.
Now there’s an environment for first drafts: no email, no web browser, no instant messenger; just you, your thoughts, and your keyboard. Going back and editing a previous line is more trouble than it’s worth, using ed (you can backspace though), so you mostly just keep typing until you’re done. Plenty of time to edit later.