A critical appreciation of a literary text is the same as a critical analysis. A critical appreciation discerns and analyses the individual parts of the literary devices that comprise a work, including non-optional literary elements and optional literary techniques. Thus a critical appreciation (i.e., analysis) will cover from structural elements to figurative language techniques and everything in between. Some of the things you will analyze in a critical appreciation of a work are:

ELEMENTS
structure
theme
point of view
characters
chronological framework (time features)
voice
tone
mood
conflict
narrator/narrative style

TECHNIQUES
figures of speech
irony
metonymy/synecdoche
imagery
symbolism
tropes
word schemes
diction
vocabulary
metaphor/simile

Concerning structure, III.iv is in two parts and set in Macbeth's banqueting hall. There are six major entrances and exits. First, Macbeth, Lady Macbeth and various Lords enter the banqueting hall; First Murderer enters but remains by the door where Macbeth approaches him; after the murderer's exit, the Ghost of Banquo enters, then exits, doing this twice; finally, the Lords exit the hall, leaving only Macbeth and Lady Macbeth. They then exit the stage themselves. The time is chronological progression until the entrance of First Murder, who introduces a flashback to the recent time of the slaying of Banquo. The mood in this scene is one of frenzy and chaos while the Lords listen in wonder and Lady Macbeth feels her panic rise. The focus, or theme, of the scene is the torments that begin to assault Macbeth as a consequence of their foul deed:

LADY MACBETH
You lack the season of all natures, sleep.
MACBETH
Come, we'll to sleep. My strange and self-abuse
Is the initiate fear that wants hard use:

Some literary techniques used include the aside, simile, metaphor, cliche and idiom. After Macbeth sees Banquo, Lady Macbeth speaks to him in an aside to question and caution him:

MACBETH
If I stand here, I saw him.
LADY MACBETH
Fie, for shame!
MACBETH
Blood hath been shed ere now, i' the olden time, [...]
LADY MACBETH
...
Your noble friends do lack you.

Another technique used is simile, as when Macbeth wonders if ghosts can really exist. He compares the apparition's appearance to a "summer cloud" that suddenly overshadows the sun and warmth of a summer's day. Another technique is metaphor. Macbeth wonders how Lady Macbeth can maintain a natural state when seeing Banquo, while he is drained of color and shattered (of course, Lady Macbeth does not see Banquo): he wonders how she can "keep the natural ruby of your cheeks, ...." One last technique I'll mention is the use of cliche and idiom.

Shakespeare is noted for his mastery of language, including the use of popular cliches and idioms. Macbeth is lamenting the appearance of Banquo's ghost and pronounces the idiomatic cliche that "blood will have blood." This saying cannot be taken literally; it has a figurative meaning that is different from the meanings of the words. While "blood" is personified and attributes the human characteristic of demanding or requiring something, the saying means that a murder will often result in another murder of revenge or cover-up. This was true for Macbeth and for the Renaissance period.

MACBETH
It will have blood; they say, blood will have blood: ....