That's a really good question! Close reading is really important because it helps you to get much deeper into the text and develop your argument so much more. There are a couple of things that you could try. First of all you should keep asking yourself 'why?' Authors and poets use specific words for a reason so always ask yourself why they have used a particular word in a sentence and what meaning or tone it adds. Another thing which always helps me is to keep a look-out for unusual words or descriptions which 'jump out' from the text. For example, in Jane Eyre, Jane describes her situation as full of "pungent suffering". The word 'pungent' is a really unusual one to use to describe suffering so think about why Bronte chose to use it: what does it say about how Jane feels?