Since Sisyphus was kind enough to ask, here's the handout I give when I start teaching explications. (And I can always use help making this better, please!)
An explication is an unfolding of a passage, a thesis-driven essay that makes an argument about how a passage works by focusing on aspects such as diction, form, metaphor, imagery, and so forth. While an explication may include a short paraphrase of the passage, the main focus is on how the passage makes its meaning, rather than what it means.
How to write an explication:
Explications are HARD to write well, but are great at developing skills in really careful, attentive reading. They do take a good deal of work, though, so give yourself time, and don’t plan on doing them at one sitting.
Here are the steps I use (and I use explication when I work on understanding a text to teach it or write about it). I do freewriting and draw in my pre-writing brainstorming because it’s important to me to have notes to work from when I start writing the essay or working on class/essay notes.
1) Read the passage. Look up words. Figure out what the passage means at a basic level.
2) Look up more words. Think about what alternatives or other words might have been used. Think about the connotations of different words and how you react to them.
3) Read the passage aloud (more than once or twice), and think about how it feels in your mouth and how it sounds. In the case of verse, you want to think about enjambment and end-stopping, rhyme and how strong it is, rhythm, aspects such as alliteration, and so forth. Are there places where the verse makes you slow down? Why? What’s the effect? Conversely, are there places where you speed up? There's no singel answer for what a technique such as alliteration "does." On the most basic level, these things make you pay closer attention, draw words together in your mind, and so forth.
4) Draw or work out imagery in some way. This is especially important for literature that describes art (ekphrasis) because there’s often a sense that talking about how graphic art works also gives us a sense of how textual art works. That is, literature about art is often also literature about literature.
5) What do you think the passage is doing? How is it doing that? Is it effective? Ineffective?
Okay, now you have your working thesis (how the passage is doing what it’s doing). Outline or rough out your argument, quoting from the passage when it helps you make your point. Develop your point with examples. You may need to reference other works (the OED, or a work on poetic techniques, if you want to talk about how metaphor works or something).
Once you’ve got your draft written, think of a title that has something to do with your argument. Don’t use “Explication” because it doesn’t help your reader get a sense of your argument.
Final notes: You probably don’t need to talk about the verse being iambic pentameter unless there’s a moment that makes that interesting. Just noting that in and of itself isn’t that useful, mostly.