I write when the urge hits me, getting the words down as fast as I can type and then I step back from what I just wrote and start a dialectical process where I begin challenging my own writing.
I do not write by any set time schedule. I realize there are many writers who follow a daily regime where they arise at 6:00 a.m., do some sort of exercise, eat breakfast and then sit down and produce words for a three to four hour period.