Depending upon the type and subject matter of the poem, I might look for any of the these things: creative use of imagery; clever alliteration (but not overdone); coherent flow; and so forth.
I don't necessarily look for rhymed verses, but I do look for "the point." Does the poem tell a story, or simply paint a picture with words? Is the meaning understandable, or is it a guessing game?
Poetry, in my opinion, is something you either like or you do not. If you like poetry in general, you may still find individual poems you dislike. That is no more than a matter of personal preference. Not everyone likes the same things.
I do not feel that poetry can be very fairly "judged" by anyone unless they have the opportunity to interview the author.
I always hated it in school when the teacher would ask, "What did the author mean?" It was all I could do to keep from yelling out, "How in blazes do I know what the author meant? I'm not inside their head!"
Poetry in many cases is a very personal expression--as such, it should not be subject to judgemental opinions. You either liked the person's poem, or you did not. And in the latter case, I feel it is better to heed Mother's old tip of, "If you can't say something nice, say nothing at all."