Write an outline for your thesis. Start by deciding on the names of each chapter, which will give you an overall structure and determine what parts of your research will go where. Add sub-headings to each chapter, which will break the chapter down into sections that deal with each part of the overall topic of the chapter.
List each topic you need to cover under each sub-heading for every chapter. This will give you an almost paragraph-by-paragraph summary of everything you need to talk about. Once you have completed this topic list, compare it with your research to make sure you have covered everything you need to cover.
Add all the images, diagrams and other figures you will refer to in your thesis in the appropriate locations. You can do this by lining up the images next to the topic notes they will illustrate. Write a paragraph or two on each topic you have listed, referring to the illustrations where necessary. Once you are done, read through the thesis to check for errors and add in any additional information you require, such as references.