Firstly, it's very important to have an excellent range of vocabulary and sophisticated grammatical structures within your given topic.Therefore I would advise including all of the basic tenses, present, past and future, to show you have an excellent grasp over the basics, and then adding more sophisticated tenses such as the conditional and the imperfect to demonstrate you are comfortable using more high-level french.In addition to this, to demonstrate your range of vocabulary, I would advise you to search, on sites such as memrise (or ask your teacher/tutor!) lists of topic-specific vocabulary for example 'holidays vocabulary' which will provide you with wide-range and even the odd a-level word/phrase which will be sure to impress your oral examiner! Make sure to incorporate these into your answers and when memorising, check the pronounciation of longer, slightly more challenging vocabulary either with your teacher or your tutor.It is equally important to be able to speak with confidence. Therefore, once you have written your answers to each question within the topic, I would advise you to memrise each answer well, but whilst memorising, try to incorporate 'French sounding' filler sounds or words: eg, instead of the english 'err' and 'well' try the french 'hein' 'bien' 'puis'. You should also try inverting questions as this will demonstrate to your examiner that you are trying to interact with him/her and hold a conversation rather tham simply listing off a (very good) but clearly memorised, and very unnatural-sounding presentation. For example, when giving an opinion, try adding 'n'est pas?' at the end, and pausing as if waiting for the examiner!All of these tips should ensure you recieve a top mark in your oral exam, so just remember, for those 5 minutes, you're no longer an english student, you're a frenchman!