A-level AQA Geography coursework advice

Hey everyone, I have just began my Geography coursework for A-level within AQA and was hoping for some pointers. I am centering my coursework around the relation of vegetation to a coastal sand dune succession, how it differs depending on the variation of the dune and how the vegetation effects the sand dune itself. I would like some advice on specific aspects of this to focus upon, as the subject is quite broad. Also, any tips or advice to gain a higher quality piece and more marks would be greatly appreciated!