Hey there!
So the way I approach the unseen texts is by directly answering the question given. You don't have a lot of time to do this, so use the question as your guide to structuring your response, and make sure you don't use all of the obvious techniques right away. Save some for the 5/6 marker at the end! To approach an unseen text, read the question before you begin to read the text. You save time because you're not straining yourself to understand the text in order to answer the question, and you're voluntarily looking more closely at the ideas that explore the concepts given by the question. Then, use the question as your structured guide.
For example, if the question was: How does this text convey ONE concept of discovery?, you can use the question itself by directly "paraphrasing" the question.
Text One conveys the unexpected nature of discovery as [idea]. As long as you've directly answered the question, you'll be good. (Also: note that the marks allocated per question is indicative of the length that your response should be. 2 marks usually mean 1-2 techniques, 3 marks usually mean 2-3 techniques, 4 marks usually mean 4 techniques, etc).
Hopefully, this helps with your question. Feel free to ask more questions, and good luck with the HSC!