I believe that your research methodology is the most important part of your research work.It is also the most difficult to write.You can't afford to do a shoddy job because scholars and advisers who go through your work lay great emphasis on this aspect.
The purpose of the methodology is to inform the readers about the methods used in your work and the statistical tool used to analyse your data.
One way to start is to look through the methodology of different projects. That will give you an idea of what a methodology section look like.
Create an outline (things that will be included in your methodology )and discus with your supervisor.
Define your research question. Your research question should not be unclear or unspecific.
Discuss the methods you used in your research in order to analyse the research questions.Your research method will depend on your topic.
State a good reason why you selected your research method.Don't just describe the method you used in conducting the research,justify their reliability and validity.
Write in a clear and concise manner.This not only show that you have a purpose but it also shows that you have a deep knowledge of the topic.