I'll second the personal deadline method. When I was writing my thesis I had a small whiteboard on my wall with a deadline for each chapter - 1 week for the shorter chapters, 3 weeks for the longest. While I didn't quite make most of the deadlines (I was usually about 3 days overdue), it was certainly much better than it would have been without the deadlines. It also helps to give the deadlines a "reason" - eg many of my friends (including myself) had flights booked for shortly after when they decided their thesis would be finished by so that there was a real financial penalty (having to move ticket) for missing the final deadline.