I unearth a poem from the stack of drafts and look at it, the veil of time allowing a shift in perspective. Then I ask myself these questions:
1. Does the title add dimension to the poem? This lecture by poet Matthea Harvey is richly educational on the subject of titles.
2. Where can I cut the fat?
3. Which details must be fleshed out? If there is a "tree" in my poem, what kind of tree? An aging spotted oak or a frostbitten cherry blossom (or maybe it really is just a "tree")?
4. How can I enhance the music of the poem?
5. Can I reconsider any line breaks? Retyping the poem can lend valuable insight. I play around with where I break my lines to see if anything interesting happens.
6. Is every single word needed? Can a more precise word replace a handful of imprecise words? I always keep in mind the economy of words in poetry.
7. Are my literary choices aligned with my poem's theme/message?
8. Is the form appropriate to showcase this particular poem?
9. Can I dig any deeper?
10. Have I done sufficient external research? If I mention a scientific phenomenon or reference an event in history I'll of course do research for that, but I also use research as a tool to enhance imagery and details in general throughout a poem.
Also check out "The Warmth of the Messy Page" by Rachel Richardson who writes in charming candor about revision, and "15 Poets on Revision" for a compilation of quotes by well known poets on the subject.