The three most important aspects for me (I'd like to emphasise that this is my opinion; would everybody agree with me?) are:
Which language forms are presented at which level; ie presenting language that is neither too easy nor too difficult. Linked to this is clear presentation on the part of the teacher.
How the language is practised: students need to be able to use the grammar they know efficiently and confidently.
Knowledge of the forms; eg present perfect = have/has and past participle. Linked to this is pronunciation and meaning.
Okay, that might be more than three! Take your pick!
I suggest you talk to your tutor about what you propose writing about and get his/her ideas about which of them are the most pertinent.
All the best