To me, good poetry contains:

 

 

Half the trouble is that if a good poem is really good, it innovates. Innovation, especially with new language, and to some extent with new form, makes it more difficult to read. And there we have the rub; a bad poem can be difficult to read. A truly bad poem can make unintentional innovation with language, and a truly annoyingly bad poem can make unintentional but interesting innovation with language. So truly bad bad poems can be rather good, actually. But they’re almost always drivel.

 

So is it worth the effort to explore a poem that's difficult to read, in the hope that it's really good, not really bad? You don’t know until you've done the work, and you won’t want to do the work unless you believe you'll get the reward a good poem gives. That's why I look for hints. And that's where understanding what contributes to a good poem comes in handy. I find that if the poem seems to be about something different, or seems to have an unusual structure, or is abusing language, then it may be worth the effort to explore properly. And, of course, if the poet has a track record of excellence, or if other people who's opinion you trust (especially editors and, to a lesser extent, critics) say they found something special in it, then put the effort in.