What leads to the alienation of Winston Smith?3 Points please, and examples from the book.

Winston Smith is alienated from others (his friends, families, co-workers, girlfriends, potential lovers and wife).  He cannot form lasting relationships because of fear.  Marriage is only condoned by the state because of procreation purposes, not for love or pleasure.  He has been bred to hate:

he thing that now suddenly struck Winston was that his mother's death, nearly thirty years ago, had been tragic and sorrowful in a way that was no longer possible. Tragedy, he perceived, belonged to the ancient time, to a time when there was still privacy, love, and friendship, and when the members of a family stood by one another without needing to know the reason. His mother's memory tore at his heart because she had died loving him, when he was too young and selfish to love her in return, and because somehow, he did not remember how, she had sacrificed herself to a conception of loyalty that was private and unalterable.

Winston Smith is alienated from the past and history. He has no sense of history.  He doesn't know what happened to his mother.  He doesn't know who his country is fighting.  He doesn't know how the world came to have 3 super-powers fighting for domination.

But to trace out the history of the whole period, to say who was fighting whom at any given moment, would have been utterly impossible, since no written record, and no spoken word, ever made mention of any other alignment than the existing one. At this moment, for example, in 1984 (if it was 1984), Oceania was at war with Eurasia and in alliance with Eastasia. In no public or private utterance was it ever admitted that the three powers had at any time been grouped along different lines. Actually, as Winston well knew, it was only four years since Oceania had been at war with Eastasia and in alliance with Eurasia.

Winston Smith is alienated from art and literature. His job is to censor words.  He's not very good "reading" people: he falls for O'Brien's obvious tricks.  He does not know what beauty is.  He thinks the coral paperweight is a work of fine art.  He thinks the old prole woman singing is beautiful.  To us, all of these are mediocre at best.  He has been cut off from all critical thinking.  Even his diary is juvenile:

His eyes re-focused on the page. He discovered that while he sat helplessly musing he had also been writing, as though by automatic action. And it was no longer the same cramped, awkward handwriting as before. His pen had slid voluptuously over the smooth paper, printing in large neat capitals

DOWN WITH BIG BROTHER
DOWN WITH BIG BROTHER
DOWN WITH BIG BROTHER
DOWN WITH BIG BROTHER
DOWN WITH BIG BROTHER

over and over again, filling half a page.