Start with the question, not the method
The chapter should open by restating what you are trying to find out, then show why your approach can answer it. Methods chosen before questions are the most common structural failure.
Justify, do not describe
Anyone can describe a survey. Marks come from explaining why a survey rather than interviews, why this sample, why this instrument. Every choice needs a reason and a rejected alternative.
Name your validity threats
Markers look for whether you know your own weaknesses. Stating a limitation and how you mitigated it scores better than pretending it is not there.
Ethics is not an appendix
If your work involves people or their data, ethics belongs in the chapter, not bolted on at the end.