MACBETH IS CRAZY
In the dagger scene Macbeth is showing signs of insanity. For example when Macbeth says the following quote he seems to believe that there is an object in front of him but its really not there."is this a dagger which i see before me / the handle towards my hand? let me clench thee."(2.1,33-34). This example shows that he is insane because he thinks there is a dagger there but there actually isn't . He also tries to clench the imaginary dagger. This proves that Macbeth is insane because he is seeing and believing stuff that is nor there or true, its all a figment of his imagination.
IF I WERE THE DIRECTOR ...
If I were a director , I would stage the dagger soliloquy by staging Macbeth center stage with a spot light on Macbeth. I would place emphasis on the lion "come let me clench thee" (2.1,34) because them i could emphasis that he cant actually grab the dagger.I woulds also hang the dagger from the ceiling out of Macbeth reach. I would place it out of his reach in away that it would be viewed by the audience more than the actor. I would do this to make it look like you are imagining what hes seeing .in the end of the play I would have the dagger disappear to prove that it was never actually it was just Macbeth's imagination.