Winston's torture and interrogation have several stages. What techniques are used in each stage?

The answer is:

Some of the main techniques used in each stage was starvation, fear, insomnia and brainwashing.

In the novel "1984," by George Orwell, Ministry of Truth clerk Winston Smith is captured and tortured by O'Brien, a member of the Thought Police which persecutes those who oppose to the rules of the government, The Party. As a consequence, Smith is exposed to intense torture for several months.