This is a general and a quick way to write a good comment on any passage that u may face:
First of all u have to read and re-read the passage many times to get the main idea of it………Secondly, u are now able to identify the title of the play, short story, or whatever it is. You are also able to identify the speaker and to whom s/he is speaking (those are the traditional steps).
You have to write about the occasion of the passage; the setting and the time; the action that leads to this one and what will happen next….
Now we come to the dramatic function of the passage; it may be the themes or the motives which are in the passage…..You have to examin the importance of the passage, the most underlying purposes that it conveys, for example: love, revenge, irony, friendship……..etc. You have to write, for example, that this passage clears the idea of desperation, frustration, Oedipus' conflict……..etc.
You have to explain the passage in your own words, and to talk somehow on the action to come but briefly.
Note: u should keep in your mind that u should not write this way:
The occasion is…………..The dramatic function is……….
You have to write them without declaring that openly, otherwise, u'll lose marks.
Finally I hope good luck for u all.........
Any specific questions on commenting, plz do not hesitate.
الله يعطيكي العافية.. 
