1. Make notes on the most likely/ striking/ memorable/ important parts of the novel, play or poem. These notes should include analysis of stylistic devices, tone, mood, context, theme, reader and author perspective.
2. Go through all of them. Some you may have to memorize or keep noted in your head. It seems tough but after reading your notes twice, you'll get the gist of what a phrase means.
3. If you get a Shakespeare play like my school did with Macbeth, use no fear Shakespeare to understand what the complex wording means.
4. Don't stress, it will cause you to lose your train of thought.
5. Give your time to relax and if you can choose the time you do your exam, I would recommend during the afternoon instead of the morning because your brain is more awake.
6. Practice your structure. Write down how you could start the introduction and end the conclusion. You won't remember exactly how you phrased it during the exam, so don't try to. Instead, having an overall understanding of the structure will help you.
Hope my tips helped! An extra advice is to not spend too long picking an extract. It won't make a difference and will just make you nervous.