These scenes are key to the play because they chart the beginning of the plan to kill Duncan and seize the crown right through to the accomplishment of this crime and then the feelings of guilt afterwards.
Act I scene iii presents us with the witches as they give their prophecies to Banquo and Macbeth. You will want to consider in particular how both of these characters respond to their prophecies and the witches. Also, a key speech is Macbeth's soliloquy when he considers his own feelings to the prophecies after finding out that Duncan has made him Thane of Cawdor - what does this speech reveal about Macbeth's state of mind, and in particular his own ambitions?
Act I scene v features Lady Macbeth reading a letter from Macbeth filling her in on what has happened. You will want to think about what kind of person is Lady Macbeth as depicted in this scene? Especially focus on her speech where she appeals to the "Spirits" to "unsex" her. Also, what does she say about Macbeth and his character? How does she view her husband and his failings? Lastly, how does Macbeth appear when he enters at last? What do we make of his final speech "We will speak further." Is this doubt or hesitation?
Act I scene vii features the famous bullying scene where Lady Macbeth literally cajoles her husband into committing the murder. You will want to think about Macbeth's soliloquy at the start of this scene. What doubts does he express? Why is he worried? What does he say about ambition? Then you will want to consider how Lady Macbeth persuades her husband. What strategies does she use to talk him into it?
Lastly Act II scene ii is straight after the event. You will want to consider how the layout of speech reflects the feelings of both Lady Macbeth and Macbeth. How are both presented in this scene? What do we make of Lady Macbeth's assertion that she would have committed the crime if Duncan hadn't resembled her father? How does Macbeth feel after committing the crime? How does Lady Macbeth respond to Macbeth? Who do you feel is more responsible for the crime?
Just some ideas to help you along. Try to answer each question and that will help you in your test. Good luck!