Actually, watching J-dramas, and news etc. are good ways to help you learn more vocabulary and also be exposed to various ways in which structures are used, irrespective of whether or not they speak in plain or polite form. It also tunes your ears for the listening component for the exam and I found it exceptionally useful when I did Japanese continuers as an accelerant.
Whilst I highly recommend you to watch or even listen to Japanese programs, I think you should also read passages of various text types that could turn up in the exam like, say, from the Wakatta textbook. Reading will help you refine the applications of the structures, learn good phrases to use - the passages are like the model which you could base your future writing tasks around. Reading will also help you learn more vocabulary pertaining to each topic. After you gain an understanding on how to write/ how certain passages are written, I emphasise you should
practice writing tasks - it all comes down to
practice. I found doing many writing tasks and getting my teacher to check it, suggest better ways of phrasing and critique it a really good way of improving my skills. This also applies for reading and responding in english - get someone to check whether you've answered the questions fully with all the required examples.
For the vocab, the above two suggestions are great ways but what you said also is a good idea. Rewrite vocabulary and memorise them. But make sure you understand how to use them and when to use them correctly, and this can be done by looking up in the dictionary for examples of the use of a particular word. It's pointless writing something you're not sure of so if in an exam condition you don't know how to use a word, I also highly recommend you to use relative clauses. E.g. If you didn't know how to say 'oil spill' you could say 'sekiyu ga umi ni takusan hairu koto' (sorry my computer doesn't have language tool). Get the idea?
As speaking was my strongest part, I recommend you to keep a small book in which you write all the answers to the questions you can think of pertaining to each topic. You should have about 2-3 sentences for each question (for depth) and have about 2-3 structures in each sentence (but no more as it would be inauthentic and too complex as well as difficult to understand, and no less as it would be too simplistic). After you write answers to questions you can think of, you should write questions which can arise from your answers. My teacher calls these type of questions "carrot" questions - your answers prompt the examiners to ask you certain questions. To clarify simply, if you are asked "What sport do you like" you could say "I like tennis...But I also like netball" and the second part of the answer would prompt the examiner to ask "do you play netball outside school?" etc. etc. Usually in an examination, the examiner will ask you simple questions and then progressively get harder to distinguish students in to bands, so practicing for every possible question will make you really prepared. As this is the speaking part, not only should you have answers to these type of questions, you should read your responses over and over again and also record yourself to listen and analyse your fluency. Practice is the way.
