How can I improve my English to French translations?

Firstly, don't rush into translating anything straight away. You should have plenty of time to complete the translation, and it's much better to think openly about what could be some good translations than to start writing straight away, which always rules out ideas. Plus, you'll have a better understanding of the passage having reading it a few times over and having thought about how you are going to translate it. Next, if you have the time, I'd recommend going through the text with a highlighter and highlighting all the verbs in every sentence. This will act as a kind of anchor for your translation into French, because the verbs are the centre of every sentence and it will help you structure the rest of your sentence around them.When you're reading through, you won't know every single word. That's not a problem - think about what broader substitute words you could use (e.g 'meal' instead of 'supper'), how you might break down the word ('walked fast' if you don't know 'ran') or words that are similar or in the same 'lexical field' (a fancy way for saying the same group of words, e.g write the word for 'pillow' if you don't know the word for 'quilt'). While you are writing, think about what pitfalls the examiners are looking out for. Finally, when you check over, always look out for gender, singulars and plurals, tenses and agreements.