Write daily for 15 to 30 minutesI can't emphasize how important this is. For one thing it builds discipline about getting something on the page everyday. For another, it does wonders to declaw the idea that writing has to be perfect on the first go-around. What I mean by this, it that it makes writing a lot less daunting if you do it habitually, and train yourself to expect that for every 10 words you write, you may end up keeping only one or two in the end. Even if you keep just that fraction, it adds up over time into lines, paragraphs, pages, sections, chapters and even dissertations. In a way, it's really just the academic equivalent of Stephen King setting daily writing goals of 1,000 or 2,000 words (King 2000), except that here you're writing to get in the habit of writing about your work, not fiction, and to fit that habit in the rest of your day.
During your daily writing sessions, don’t think about your final manuscript. Just write journal entries, says Tara Gray, director of the teaching academy that provides training and support to New Mexico State University professors. “People think there’s two phases of a research project—doing the research and writing it up,” she says. Rather than setting aside large chunks of time for each activity, combine them to improve your writing and your research. The first time Gray encouraged a group of faculty members at New Mexico State to adhere to this schedule for three months, they wrote about twice as much as their normal output.
This is incidentally the key piece of advice from J. Bolker's Writing Your Dissertation in Fifteen Minutes A Day (Bolker 1998). I rarely recommend books as must-reads for graduate students, since everyone's trajectory and style is so different. Bolker's book is one of the few exceptions to this general rule: it really does a wonderful job of showing the importance and, frankly, the healthiness of making writing a routine exercise as opposed to something that is better saved for intense bursts. Now - spoiler alert - the book doesn't actually show you how to write your dissertation (or thesis, or paper, or whatever) in 15 minutes a day. But it does provide a really clear framework for how to think about and structure your writing, and especially developing healthy writing habits. And the key thing about this is also what T. Gray mentions in the quote above: in my experience, approaching writing in this way does allow you to write more and write better overall. It also provides you with a much better use of your time for those 15-30 minutes 'dead periods' between classes or meetings than just surfing the net!
That said, I don't know about the 'journal entry' approach advocated by Gray, but to each is own. Frankly, the important thing is really just to write something, anything daily. It may sound silly, but for a great many people, it works and it helps make the whole process of academic writing that much easier and, dare I say it, appealing.
Bolker, J. 1998.Writing Your Dissertation in Fifteen Minutes a Day: A Guide to Starting, Revising, and Finishing Your Doctoral Thesis.Owl Books, NY.
King, S. 2000. On Writing: A Memoir of the Craft. Scribner, NY.