Writing a thesis / dissertation takes much time, which is why it is recommended to organize your work straightforward from the very beginning. Here are some recommendations: - You should keep careful notes about your work. Even if some of the notions and ideas seem waste, you should reconsider them later and your notes will be helpful at this point. - As soon as you have printed a draft of a chapter you will understand that some changes are necessary. The second draft will be surely also changed. So after some time you will inevitably face the problem of sorting out which of the drafts is the latest one. The best solution is to print each draft of your dissertation / thesis on a different color paper.