Poetry does not need to be approached as though the reader is a WWII codebreaker and the success of the Allied war-effort is at stake, although one does need to have some familiarity with the common elements of poetic language. Tony Hoagland has a website/seminar (called Five Powers of Poetry) for teachers of poetry which discusses some of these key elements in relatively simple, straightforward language. It's well worth looking at if you're interested in poetry but have been taught to fear it.
The first of these five powers is IMAGE.
In my stripped-down, non-academic approach to imagery, I think of three main kinds of image-making, although I'm sure there are others:
From Jane Kenyon's poem, After the Dinner Party :
A late-blooming burgundy hollyhock sways
across the kitchen window in a light breeze
as I draw a tumbler of well-water at the sink.
This is a good example of descriptive imagery. It serves to set the scene of the poem as well as the tone and voice of the poet (quiet, conversational, domestic). By itself, it's power is substantial but limited.
This is the 'like' or 'as' statement most of us are familiar with from English 101. Sticking with Jane Kenyon for now, from her poem, At the Public Market Museum: Charleston, South Carolina:
A volunteer, a Daughter of the Confederacy,
receives my admission and points the way.
Here are gray jackets with holes in them,
red sashes with individual flourishes,
things soft as flesh. Someone sewed ...
Here is a good example of how simile is just that much more powerful, that much more evocative than pure description, how it can further the poetic intent just that much more.
By the way, notice the power of a good line break as well, which I've included after the simile. The line can then also be read, "things soft as flesh someone sewed" which adds another layer of meaning (sutured up after being shot?) without saying anything directly.
The grandaddy of imagistic mechanisms. Imagery on steroids, if you like. Milan Kundera, author of The Unbearable Lightness of Being, says it well:
Metaphors can be created by the clever use of a single word (e.g., verb or adverb) as in Kenyon's poem, Walking Notes: Hamden, Connecticut:
My daily walk takes me past a house
where roses scramble lustily
up the trellises ...
Here, in the personification of the roses which scramble lustily, she suggests a sexual energy, a primal urge that contrasts starkly with the staid, suburban neighbourhood she is exploring.
And from Last Days:
Over the orchard a truly black cloud appeared.
Then horizontal rain began, and apples fell
before their time. Leaves blew
in phalanxes along the ground.
Here, Kenyon, in this poem about the illness and impending death of the subject of the poem begins the poem with imagery of battle, of war, with the apples falling like young soldiers and the leaves moving in phalanxes, which are columns or tight formations of soldiers. But here's where metaphor gives the poet the most bang for the buck: phalanxes are also bones in the hand and it is almost as though the leaves are also the bony fingers of Death coming to claim the subject of the poem! The use of this imagery says things within the poem that the poet cannot, at least not without sounding simplistic and overwrought.
So when next reading poetry (and I hope it will be soon!) keep an eye out for the imagery of the poem and notice how it sets a mood or establishes the voice of the poet or how it might further the event of the poem. But even it you can't figure out what the poem is about, many times the images by themselves, in the way they make you feel or through the other images and thoughts they conjure in a kind of poetic chain-reaction, make the poem enjoyable and worthwhile!