When writing about a single memorable day in your life you need to consider important facts to mention and remarkable moments. For example: a special birthday celebration, a graduation day, a special visit, etc.
Then you need the setting, day, weather and write about why it was so special for you.
You must remember to describe clearly what happened why is it funny or not and to show why you want to write about it.
Finally in your conclusion you can add some anecdote that makes it a remarkable and unforgettable day and what you liked the most of it.
Mr. O'Brien and Winston are the principals starrings of the novel.
Textually O'Brien tells Winston: The first thing you must realize is that power is collective. The individual only has power in so far as he ceases to be an individual..alone...free.. the human being is always defeated.
That is the first thing from O'Brien to Winston.