The thing that has helped me consistently get -1 or -2 on the problem sets has been to read the passages very carefully. Pairing this with the short summaries of each paragraph helped me gain a better understanding of what was being explained/argued for etc. in the passage. While it may take a little longer to get through the passage itself, it has helped me be much quicker on the questions as I do not have to go back and read sections of the passage I did not understand at first. Hope this helps!