How can I ensure that I demonstrate a wide range of skills in such a short space of time (i.e. during an exam) in order to achieve higher marks?

I find the most effective way to ensure that you show off all of your skills during a short period (such as an exam) is to create a checklist of stock phrases that you can memorise and use during your exam. For example, for a GCSE French writing paper, I could recommend this tick list of stock phrases in order to make sure you manage to cram in all the tenses for a higher mark; -Present - j'aime... -Past imperfect - quand j'étais pétit... -Past - j'ai joué... -Future - j'irais -Conditional - je voudrais -Subjunctive - bien que je puisse voir pourquoi certains pensent que... personellement, je crois que... You could abbreviate this list to 'PPPFCS' and write this acronym on your paper at the beginning along with the stock phrases that you have learnt by heart. (These stock phrases are examples of each of the skills listed that can be applied in most situations so that if you panic about conjugating during the exam, you can just remember one specific example to demonstrate your skill - if the examiners see one example of the subjunctive, they don't need to know whether you conjugated that off the top of your head or not!) When you are checking through your exam at the end, you can run through your PPPFCCS list and tick off each one you've managed to put in your piece of writing, and double check you've not missed any. This will ensure if you forget how to conjugate any of your tenses/are unsure of your conjugation/require more examples, you can just remember your one set phrase - and there you have it, you have shown the examiner that you can use it effectively!