Shakespeare does not describe Juliet's death. He was not writing novels.
The stage direction which follows Juliet's line "O happy dagger. This is thy sheath, there rust and let me die." in the Folio version of the play is:
"KILS HERSELFE" (sic)
In the first Quarto of 1597 it says
"SHE STABS HERSELFE AND FALLES"
And the second Quarto of 1599 has no stage direction at all.
Obviously Shakespeare uses no imagery whatsoever to describe Juliet's death. And why should he? The audience can see it happen. A picture's worth a thousand words.
Shakespeare uses vivid imagery to describe Juliet's death in a tragic and detailed manner. He often employs dark and ominous imagery, comparing Juliet's life to a candle that is extinguished or a flower that withers. By using such imagery, Shakespeare conveys the emotional weight and finality of Juliet's death.
Throughout his play, Shakespeare uses death to move his story along. He does this with actual deaths, which cause problems for the lovers, and through premonitions and dreams of death. Both Juliet and her Romeo exhibit these premonitions/dreams.
The literary term is metaphor, specifically a metaphor where Juliet is being compared to the sun. Metaphors involve describing one thing in terms of another to create vivid imagery and deepen meaning in a text. In this case, Shakespeare uses the metaphor "Juliet is the sun" to emphasize Juliet's beauty and importance in Romeo's eyes.
Metaphor
Lord Capulet uses personification in the quotation "Death lies on her like an untimely frost upon the sweetest flower of all the field" to describe his daughter Juliet. Personification is the attribution of human characteristics to non-human things, in this case, death is being described as lying on Juliet like frost on a flower. This metaphor emphasizes the sudden and unexpected nature of Juliet's death, highlighting the tragedy of the situation.
motif
The excuse Juliet uses is that she is going to Friar Laurence's cell for shrift or confession.
In the play he uses a rope ladder that the nurse brings to Juliet's balcony for him. In the movie he just climbs up a tree.
Act I, Scene 3, Lines 79 - 94. How the Nurse and Lady Capulet speak of the qualities of Paris. They add to the previous metaphors creating an entire monologue of an extended metaphor. see how: http://nfs.sparknotes.com/romeojuliet/page_44.html
Yes, Shakespeare uses several asides in Romeo & Juliet. Reade the play to see specifically when and where.
She kills herself with Romeo's dagger.
Juliet