How would I do a close reading of an unseen extract?

You would want to look at three key aspects: language, structure, and form. In terms of language, you would look at what meanings and associations certain words choices make. You could look at metaphors, similes, wider imagery, or personification, and explore why you think the author chose to use language in this way, and what effect this creates: each word was chosen for a reason. For structure, you can first look at wider narrative structure, exploring techniques such as foreshadowing, and anti-climax/climax, and asking why the author chose to order the narrative events in this way. You might want to question what would happen if the narrative events were in a different order, and use that to rationalise why the author chose their order. You can also look at smaller structures on a sentence level, looking at word order (syntax) and repetition, and what effects you think these create. Finally, you can think of form as the 'type' of text, the packaging it comes in. Is it from a novel, a play, a sonnet, an epic poem? Then ask yourself why you think the author chose this kind of packaging for their themes/subject matter, and what the form allows the text to do (for example, a poetic form allows for rhyme and meter).