What literary devices does Robert Frost use in "Stopping By Woods on a Snowy Evening"?

There are a couple of poetic devices used in this poem by Frost. In the first line, Frost inverts the normal sentence structure of the line: "Whose woods these are I think I know" instead of "I think I know whose woods these are." This switching of regular word order first helps with the rhyme scheme that he keeps throughout the poem, but since it is the first line of the poem, it also catches the reader's attention. Frost could have started the poem in any fashion and matched the rhyme to that first line; he chose to invert it from the start.

There is also personification of the speaker's horse, who "must think it queer" (5) that the speaker has stopped so suddenly, and who "gives his harness bells a shake / To ask if there is some mistake" (9-10).  

Finally, Frost uses alliteration to create the sense and sound of snow falling in line 11: "The only other sound's the sweep." The "s" sound created by the repetition gives the sense of quiet that a snowfall would bring.