The epigraph of the poem is an excerpt from Dante's Inferno, in which that the perfect audience could only be someone who would never be allowed into the real world where that person(s) might reveal Prufrock's idiosyncrasies. This of course is impossible so therefore he must settle on a personal reflection, thus creating an interior dialogue. This in effect sets a mood of isolation giving the reader some foreshadowing in to what the poem will be about.
The image of "a patient etherized upon a table" and "half-deserted streets" gives a more gloomy setting and adds to the isolation set forth by the epigraph. On lines 55-58, Prufrock compares himself to an insect being on display for all to poke and prod. This is how he will feel if he where to ever try and talk to one of the girls that he is so fascinated with. The yellow fog described on lines 15-25, refer to a giant cat spreading into every crevice and nook, spreading out enveloping everything in its path; the color yellow is used to show the fog is somehow tainted giving the feeling of being smothered.
The lines "In the room the women come and go talking of Michelangelo" are repeated because it is this person that Prufrock compares himself to. Michelangelo did many paintings and sculptures and was involved with the church giving him and his work a divine quality, Prufrock on the other hand hasn't done anything of the sort. In the eyes of Prufrock he could never compare with Michelangelo, therefore he could never be the object of the women's conversations much less their desires or hearts.
The repetition of the lines "how should I presume?" and "how should I begin?" exemplify Prufrocks inability to commit and his overall pessimistic outlook....