Translation is a tricky business, endlessly requiring perfection and fine-tuning. However, in the confines of an exam translations sit between two extremes: literal, word-for-word translation which is more stilted; and more fluent translation in better English which is less tied down to the literal meaning of the text. Getting a good mark in an exam is about balancing your translation between these two extremes.
The first step is always to make sure you are confident with the grammar and vocabulary of the sentence. Before writing anything down, identify and parse every word and its position in the grammatical structure in the sentence. The result of this should be an accurate, literal translation. This will get you a good mark, but not a top one.
Then take a step back and look at the context of the sentence. Ask yourself: what is the passage about? Where is the passage leading? What is the tone of the passage? Try to find English language that mirrors the tone but also sounds better in English. This can also be done for the structure of the passage. For example, Latin and Greek’s tendency towards longer sentences can lead to awkwardly long sentences in a literal English translation – look for breakpoints where you can cut the longer sentence into several sentences in English.
One caveat to a free-flowing translation is that it must continue to demonstrate that you have understood every word and grammatical structure in the passage: you cannot go so far off-piste that you change the meaning of the original. As ever, practice makes perfect – the final tip is to do as much translation on as many different types of passage as you can. Good luck!