What is the best way to memorize Robert Frost's "The Road Not Taken"?

The best way to memorize a poem is to find key features of the poem's structure that create a pattern to you or stand out to you. These you will remember, so construct your memorization around them.
In Robert Frost's "The Road Not Taken," there are connections of ideas in each stanza; there is a chronological design: 
The speakers sees the two paths [roads] and looks down one of them
The speaker takes the other path because it was grassy and not worn, although they look essentially the same
He keeps the first "road" for another day
He will tell "this" with a sigh
Once you get these ideas in your mind--the main ideas--along with their pattern, you can memorize the first lines of each stanza thoroughly as they will "ignite" your memory of the ones that follow.
If you can easily learn songs, then committing to memory the meter of the poem and its rhyme is a good way to remember it. (Some students memorize the last words of each line, rather than the first.) Reading the poem aloud over and over will assist the "ear" to remember the lines.-OR-Since poems often progress through associative images, you can write down these images and look at the words as you begin to memorize. Sometimes when a student gets "stuck," these images will ignite the memory. Memorizing key phrases helps, also, as they act as connective tissue.
-OR-Memorizing the first letter of each line, or the first word, helps to "jog" the memory sometimes. This is very helpful if students are asked to write the poem from memory, since they can quickly write those letters down, then fill in the poem from the beginning. Often that one letter will jog the memory.________________________________________________
Read the poem aloud several times and practice, practice. Nothing is better than repetition. Hearing it helps, too. As the lines become more familiar to you, say them without looking at the page. Then, see if you can write it without looking at anything.
https://masterofmemory.com/poetry/