Firstly, during/after watching a live theatre performance, I suggest taking notes under the headings of 'costume' 'character performance' 'staging' 'lighting/sound design'. I suggest this as then all your ideas during and shortly after the performance will not be forgotten by the time you complete your essay! Live theatre is all about drawing connections between your Drama text and the live theatre you have watched. You then explain how these performances would influence your own ideas as an actor, director or designer. Although, what many forget is that live theatre isn't always about what you liked and would take from a performance, but you can also say what you disliked and how this inspired you to create something different for your own version of a performance/piece!