To be a poet (#5 in a possibly infinite series)

Build a poem from start to finish.

It's possible to just throw together words and get a decent poem but mostly it doesn't work well. It's better to have a beginning and an end, with changes or transitions in between. The changes can be in tone, or in word choice, attitude, point of view, or any other element.

One way to look at it is in terms of narrative arc (even for non-narrative poems, though in those this is more metaphorical). There is usually some kind of set up. In a poem this may be introducing the subject, or the point of view, or the prevailing imagery. Then, there is some exposition of conflict or scenes along a journey. Then there is resolution, some revelation or question that ties it all together.

Though poetry has no iron clad rules, this gives you a powerful lens through which to view a poem. Where does it start? What imagery, emotion or scene is used at the beginning? How is that element (scene, emotion, image, etc) different at the end? Is there a progression from the first to the last? Is the progression tight or loose? (Or so unclear it needs revision?) 

Consider the "narrative" structure of a poem both in reading and writing poetry. It helps see the poem as a whole, rather than just a bunch of lines.