Remember you have only 90 minutes to get through the ELAT, and structure accordingly. Be familiar with your strengths beforehand: are you more comfortable analysing prose or poetry? Spending too long making a decision on your choice of analysis can cost you valuable time. Read through all of the material once; make a swift decision as to which two you can compare. If you see a writer you've studied before in class, pick that. This means you are already familiar with their style and techniques and will be able to discuss it well.I would advise that you pick two texts rather than three so as not to spread yourself too thinly over the time given. Make a brief plan in which you compare and contrast the central themes from the two writers in each paragraph. Once you've got a basic plan, write swiftly, and try to leave some time for drafting your conclusion at the end. You want to leave the examiners with a good final impression!