Manipulation occurs in George Orwell's 1984 when the government, also called Big Brother, inundates society with misinformation. News is manipulated for effect, there is no free press. When the government can control production and dissemination of the news, citizens cannot benefit from a free exchange of ideas. It makes people a lot easier to control.
The government actually does even more than that—it actively changes history, going so far as to rewrite news articles from the past to support actions taken by the government in the present.
In Macbeth, most of the manipulation is perpetrated on the character of Macbeth. He is a great warrior, but not very bright when it comes to understanding the motivations and actions of others. His wife, Lady Macbeth, is actually the more ambitious of the two, and she skillfully persuades him to do the unthinkable—kill King Duncan, so that he can become king himself. She does this by attacking his ego, suggesting that he is not really a man if he cannot stomach the idea of killing Duncan. She also behaves as though he would be disloyal to her if he did not kill Duncan.
Macbeth is also manipulated by the witches, who show him prophecies that entice him to gain power, then commit violence to keep it.
Left to his own devices, Macbeth would probably have passed on killing Duncan and seeking the throne. At one point he has decided forgo the whole thing, but Lady Macbeth talks him out of it.