You could try finding some Quizlets to help you memorise the key vocab, there are ones with pretty much all the vocab you need to know on them. Also, I would recommend learning your tenses really well for the writing - to get full marks I believe you need 5 correctly used tenses, so you could use any from present, near future, distant future, perfect, imperfect, recent past, subjunctive, pluperfect, conditional, past conditional - you can also repeat yourself a lot in the writing because different questions are marked by different people, so if you have one or two really good phrases you can use them in both. You also need to give a couple of opinion phrases and use two or three interesting structures e.g. Apres avoir, avant de, il est important de, ce qui est plus important pour moi dans La vie etc.
That should boost your grades by a lot.
I hope this helps