How do I find literary devices in "The Road Not Taken"?

One of the simplest literary devices to find in this poem is imagery.  Imagery refers to sensory experience represented through language.  So, any time the speaker describes something that you can see, hear, taste, smell, or touch, the poet is using imagery.  We can identify the first line as imagery, then: "Two roads diverged in a yellow wood."  The leaves are all yellow, telling us that it is fall, and there are two roads that split away from one another between the trees. 

We can also identify symbolism in this poem, if not before the final stanza then in the final stanza.  The speaker equates one road with having made "all the difference" in his life (line 20).  Although it is lie because he has already said that both roads were "worn [...] about the same," it shows us that the roads have more meaning that just their literal one (10).  Thus, we can understand that the roads symbolize choices in one's life.