Deductions

Hello, I am stressed because I cannot make deductions the way the instructor makes them. For example, the deduction in the Question Setup video, where the instructor says "L/M" would be in Q. When she explains it, I understand it clearly, but I cannot bring myself to think this way unprompted, and of course with the time limitations on the actual test, I don't have time to contemplate these "hidden" deductions. What can I do to make these advanced deductions on my own? It helps the game a lot and ultimately saves time, but it's just hard to bring myself to think in that way.