1. Before the actual defense, do at least one dry run in front of trusted friends or colleagues who can give you honest and helpful comments.
2. Before your defense, take some time to become familiar with the particular areas of research interest held by the members of your examining committee. Write down some of the questions you think they might ask and formulate your answers. Then get together with a fellow graduate student. Ask each other the questions you think the examiners will ask, and practice your answers until you feel comfortable with them.
3. At the beginning of the oral defense of your thesis, you will have an opportunity to give a brief (e.g. 15 minute) synopsis of your research as a presentation. Consider what you want to include or mention. Think about what parts of your thesis are essential for your examination committee to hear, and what parts are less important. Ask yourself how you can explain these essential aspects clearly? Do you need to use visual aids? Should you use slides with the components stated in point form? Would a flow chart help?