There are two schools on copyediting poetry. The first school says “Don’t! Change! A! Thing!” and the second school says “AAAHHHH, there are no periods on the page!!! And it’s center-justified!! And Chicago doesn’t give you any advice at all!!!”
Stop freaking out, people. There is a middle road. While you should never wade into a poem and change phrasing just because something is not strictly by the book (by which I mean Chicago), that doesn’t mean you can’t query the author. But be prepared for the poet to have an informed, impassioned explanation as to why she needs to invent symbols.
There are two main guidelines to editing poetry.
Query inconsistencies.
When poets edit their own work, they read for the imagery, the effect, the line breaks, etc. Most of them are not going to notice that the three adjectives in the first stanza are separated by commas while the list of adjectives in the last stanza has no commas at all the way they might if they were working in prose. So you, good copyeditor, must point it out to them.
This brings in a larger issue of punctuation. I like to call this the e.e. cummings defense. The poet might use Cummings to defend their laziness, but seriously, is he as good as my friend Edward Estlin? Unlikely. Most poets should use punctuation sensibly. And if their punctuation is dodgy, they damn well better have a good reason for it.
Then there is the gratuitous capitalization. One of the more charming things about writing poems in Word is that Word often takes it onto itself to capitalize the first line of each line as if you were writing a list. So, as a copyeditor, if you notice that lines are inconsistently capitalized, you should definitely query.
Use a light hand.
Poetry is not a place to be a prescriptivist. It might make you crazy that the poet has not put in any articles, but for the love of god, don’t add articles in front of the nouns. Seriously. Practice a little live and let live. Just try to keep things consistent. As mentioned above, poets often have a reason for their madness. Sometimes the reason isn’t crazy or based in drunken ramblings at 2 a.m. either. You wouldn’t take Jackson Pollock to task for not painting in straight lines, now, would you?
Fangs and Clause 
But if the reason alludes you and creates too much conflict in your CE spirit, take a short break and try looking for your own inner Jackson Pollack. Visit http://jacksonpollock.org/ for a spell. It might make you (at least temporarily) more indulgent.
“Alludes”? What could you possibly mean? No copy editor, you.
Just wondering if you would create a style sheet for poetry, or if it’s dependent on the length of the poem, or not at all, because of the inconsistent nature of poetry? Thanks very much!
That’s an excellent question. If I were copyediting a longer MS (more than one poem), I would create a style sheet so the poet would be consistent throughout the book/chapbook. There might be some resistance from the poet, so I would do it with a light hand and/or be flexible about it. If the poet italicizes someone speaking, for example, she should probably do so throughout, so the reader knows what to expect.
I suppose if it were just one poem, you’d want to be consistent too. I’m a big fan of using punctuation correctly or not at all in a poem. There are rules of reader expectation in poems, just as in all other forms, so the poet should at least consider them.