The way in which the government in this future dystopia keeps control over its people is through a combination of manipulation and fear. There is of course the ever-present threat of the Thought Police, which Winston makes clear in the opening chapter, who are able to watch everybody all the time and see into their minds. Then there is the way in which the Party turn families against each other, with children reporting their parents to the authorities for the slightest crime. The Party's assault on families does not only seek to separate parents from children, but also wife from husband, as it attacks sex itself, making people think it is merely a functional necessity rather than a physical act of pleasure and love. Finally, and perhaps most importantly, it is shown through Winston's job in the Ministry of Truth that a vital way in which the government maintains control is through its iron-grip of what happened in the past. Note how this is explored in the following quote:
And if all others accepted the lie which the Party imposed--if all records told the same tale--then the lie passed into history and became truth. "Who controls the past," ran the Party slogan, "controls the future: who controls the present controls the past." And yet the past, though of its nature alterable, never had been altered. Whatever was true now was true from everlasting to everlasting. It was quite simple. All that was needed was an unending series of victories over your own memory. "Reality control," they called it: in Newspeak, "doublethink."
This shows how the Party owned or controlled the "truth" of what happened in the past through its constant shifting of historical realities and the various "unending series of victories over your own memory." It is this that allows the Party to shift allegiance in the war without anybody taking note, and suddenly to have always been opposed to one particular side. The name that is given to this process, "Reality Control," shows how through this method the Party is able to literally control reality and people's perception of it, which is the most effective method of maintaining power over its populace.
Then how does the party control the people by using technology (telescreen, etc.)? I need to write a five paragraph essay about it, and I find it hard what to write about for the three body paragraphs..
Telescreen is a more obvious means of control. The problem with telescreen is that it goes in both ways, you can see the transmissions, but you can also be seen through it, and someone usually does watch. You have that scene where Winston does morning exercises with a group of people, these exercises are obligatory and when he stops for a moment the instructor from the telescreen calls out to him (using the coded number he was appointed) and tells him to work harder. Imagine if you were watching the news eating in front of the TV and the broadcaster stops to tell you not to eat in the living room. Also, at the very beginning of the novel when Winston writes down: "Down with the Big Brother" he has to find a place in his apartment that cannot be seen by the people behind the telescreen.
Apart from manipulation and fear, the final stone in this pyramid of a tyrannical government is pain. Winston is finally broken when threatened with face-eating rats (although this threat of pain is much greater to Winston inasmuch as he is afraid of them). The combination of fear and excruciating pain causes him to betray his love for Julia. Orwell sends a message that our instinct for survival is far greater than any other emotion (good or bad) we might harbour within us.