The 4 themes I have decided to pick are:Control, jealousy,love,obsession
Take a plain piece of paper or open a new word document, and write four headings - "control", "jealousy", "love", and "obsession".
Make a bullet point list of the main points you want to discuss within your discussion of these topic areas, then add two or three key quotes that you could use for each of these points.
Organise these points into paragraphs, probably (in your case) by theme - so one paragraph for each of your chosen themes. Be selective - a point about "this person is happy" is not as good as "this person is happy because...", but again, that is not as good as "this person is happy because... and this implies...".
Within each paragraph (or theme), put your points into a logical order. Start with a relatively simple point, then your next point should lead on from that, but develop it, until your meatiest point, which should generally go at the end.
Then, you only need to make a list that might read "Obsession - Character B talks about Character C in this obsessive way - this implies obsession - this is developed by the author through language on page 45 - which contrast to the other author during the scene between these two characters - this can be seen to demonstrate the pain brought about by obsession" into a paragraph with developed and coherent sentences.
Remember to use topic sentences at the start - for example, "in this book, this author presents Obsession as a prominent theme" - and always link back to the question at the end.