First, read the extract slowly and thoroughly. Try to get an overall sense of it. What is the tone? You will need to construct an argument about what the extract is trying to do.
It is important to be able to identify a range of literary techniques. When looking at extracts in past papers, practise finding alliteration, metaphor, foreshadowing, unconventional syntax and more. Read the language closely. Can you see any individual words which really affect the tone of the writing? When you find these features, neatly annotate them so that you can refer back to them later when you start to plan.
However, this alone is insufficient to gain you marks. Don't just spot literary techniques; you will need to explain how they are achieving the extract's overall purpose. Does the writer seem to be subtly ridiculing a character? Perhaps they use sophisticated language which contrasts with that character's foolish actions, emphasising how silly they are. Always link the techniques you find back to your overall argument.
Your plan does not need to be in full sentences. As long as it will make sense to you when you start writing, it's fine to use shorthand as this will save you time. Divide your ideas into clear paragraphs. Start by planning your introduction - this sets out your argument. Next, plan the body of your essay. Each paragraph should be about a different idea and it should broadly follow this structure: state which technique you are going to write about, include a quotation and explain how this supports your overall argument. Finally, plan your conclusion: a brief summary of the points you've made. Try to compare and evaluate a little. Of all the techniques you've talked about, which were most effective in achieving the writer's purpose?
When you have a rough plan, start to think about your context and secondary reading. How can you incorporate it into this essay? Maybe you can remember reading a poem which used a lot of death imagery, just like this unseen extract. Maybe something in the text is characteristic of the time period. You can then make notes in the relevant sections of your plan to remind yourself to mention this.
What about alternative arguments? If you can think of more than one way to interpret something, say so! It can be as simple as 'some readers might feel that ___, while other readers ___...' but will be much stronger if you can be more specific. How might some feminists read this text? Would modern readers feel differently to readers of the time? Again, add these notes to the relevant sections of your plan. It's important to show the examiner that you are considering different readings of the text.
You should now have a strong plan you feel confident in and be ready to start writing your essay! Practise this method on as many past papers you can find. The more you do it, the easier it will be to remember, and you won't have to worry about missing something important out in the exam. You should have plenty of time, so take a deep breath and work at a comfortable pace.