I actually cannot believe that I have written a few paragraphs (very, very, very rough paragraphs) for my discussion chapter. The final chapter of the PhD thesis. The last frontier. While you will most likely just want to dive straight into the discussion chapter and finish it as quickly as you can, I have a few tips before you get started.
1) Read other theses- Read some other PhD student theses and focus on their discussion chapter to get a feel for what other people put in their chapter. Everyone structures them slightly differently, so reading a few different ones is important.
2) Plan- Plan out the sections of your discussion chapter- This way you know what to include and can focus on writing one section at a time. I wrote out all my headings and subheadings before I started writing.
3) Discuss the plan with your supervisor- Run the plan past your supervisor(s) before you start. You want to ensure you are including all the relevant information while not including too much!
4) Pen & Paper- Start writing the sections of your discussion chapter using pen and paper (old school, I know) and without your thesis in front of you. You should be able to write down the key findings, strengths, limitations, and future directions without looking over the other chapters. You have lived and breathed your thesis for years and you need to trust that you know it. Writing the discussion chapter blind is a great way to practice for your Viva. Obviously after you have completed the draft paragraphs you can check these against your thesis.