Your speaking exam is a time for you to excel, and to show off your knowledge of the language. So, in preparation you should make lists of specialist phrases and vocabulary that can easily fit into conversations to provide you with boosts in marks for complexity. For instance, utilising the subjunctive tense is a sure-fire way to do this and easily fit this complex conjugation in through mere memorisation, through such phrases as: il faut qu'on souvienne que ... (= it must be remembered that). Also, you can use idioms, a range of tenses, adjectives and exclamatives to really show your enthusiasm and your complex knowledge. Additionally, you need accuracy to go hand in hand with the element of flair through your language, therefore you need to practise the language you feel comfortable with using/that is in your range in order so that you keep accuracy throughout your speaking, as this is more important than any fancy phrases! Finally, you need a developed and trained accent to give you greater fluency marks, and allow the conversation to flow at a normal speaking pace.