Question

According to lady macbeth's plan, how will the king be killed?

Answer 1

According to lady macbeth, she thinks that they should drug the guards and that macbeth should kill King Duncan on the night that they celebrate.  This way, Macbeth would become King

Answer 2

Lady Macbeth's plan is that Macbeth with kill Duncan with daggers that she herself places in Duncan's room. Once a bell sounds, Macbeth will know it is safe to kill Duncan because Lady Macbeth plans to drug the guards not only so Macbeth can commit the crime, but so that they can pin the crime on the guards by leaving the daggers with them and smearing them with blood.

Hope this helps