Write an introduction, which presents the focus of your research. Begin with the big picture and work your way down to specifics pointing out what is already known and what questions remain to be answered, as well as why it is important. Outline the problems or questions you intend to address with your research, and briefly, your approach. The introduction should be at least four but no more than 10 pages long.
Construct the body of the dissertation. If you are in the sciences, each research project should be a stand-alone chapter. Put these chapters in a reasonable order, beginning with the first, or most basic and question you addressed. Gradually get more complex with each chapter. There are no limits to the length of or number of chapters in a dissertation. But, each chapter should, depending on the field, have at least the following sections: introduction, materials and methods, data analyses, results, discussion and references.
Write a conclusion. By the time you finish your dissertation, you are the expert on the subject matter you studied. Summarize your findings, beginning with the smallest details. Gradually focus your shift outward until the last few paragraphs end with what your research means in a bigger framework. Notice, this is the opposite of what you did in the introduction. Make the conclusion chapter approximately as long as the introduction chapter.
Write acknowledgements. In this section, which should be no more than two pages long, thank all of the people who assisted you during your graduate studies. Usually this includes your major professor, committee members, field or laboratory technicians and even family members. This is also the place to acknowledge any sources of funding you received.
Design a table of contents. Although this will go in the front of the dissertation, it should be the last section written. By the time you write the table of contents, the rest of your dissertation is finished and you can assign page numbers. Include the introduction, conclusion, each chapter and the acknowledgements. It is also useful to include tables and figures.