For the most part, their response is to redirect their anger in a way that the Party allows and encourages. This is what the "Two Minutes Hate" are all about. People who are frustrated because they're oppressed are having their reactions channeled against an "enemy," principally Emmanuel Goldstein, the semi-mythic symbol of heresy against the Party. The demonstrations, such as the one Winston participates in when the announcement is suddenly made that they are now at war with Eastasia instead of Eurasia, are another example of a public display where people can act out their aggressions "harmlessly," which means by not defying the Party and instead shouting their support of it. In individual cases, we see surreptitious and inner rebellion, like when Winston and Julia engage in their secret affair—a kind of blasphemy in this sexually repressed world. Others, like Parsons, respond by being completely submissive, acting as if the Party and the whole system are great. An intellectual such as Syme responds by becoming a complete devotee of Party ideology, hating "heretics" with a restless zeal although he's presumably smart enough to know, better than anyone else, how ruthless and destructive that ideology is, since he eventually becomes a victim himself and is "vaporized."
The entire system and way of life are one huge, universal form of oppression, so it's difficult to identify an isolated event or action which one person in Oceania is reacting against—that is, until Winston and Julia are arrested. We then have the opportunity to see not merely the responses of Winston, but those of other people in the holding cell with him. Everyone is stunned and terrified. Even though they know they're finished, none of these people have the courage to get up and shout their defiance. No one is like the chained man Kostoyed in Doctor Zhivago, who shouts to the others on the train, "I'm a free man! Long live anarchy!" They are either silent, like Winston, or befuddled, like Ampleforth and Parsons. Winston himself inwardly explains this phenomenon of either silence or denial when, after a devastating blow to him from the guard's truncheon, he reflects that in the face of physical pain, "there are no heroes."