In Orwell’s much cruder world, such things were normally obtained by imprisonment, torture and threats of death. Some more backward states still use these methods, presumably because they are as stupid as they are malign. Do they really need to?
In our marshmallow totalitarianism, the threat is usually much softer – the dissenter’s job and standing are threatened, and if he does not give in, his livelihood and his reputation are taken away.
Instead of the torture machine and Room 101 in the Ministry of Love, the Twitter Mob, howling with execration, incessant and relentless, frightens most bodies into sacrificing the necessary victim. It seems to work. The chosen individual suffers, but everyone else soon gets used to it.