If you're writing a poem it's essential that it sounds lively - which doesn't mean it has to sound like all the other poems you've read. Often people make their poems too 'poemy', so that their language sounds tired. Language in poems should never be tired. It should sound as if it's just woken up.
What keeps poems on their toes is the line-endings. Whether or not they rhyme, they should always supply energy to the poem as it moves along. What is the most obvious difference between poetry and prose? The importance of the line endings.
Poems are as close as language gets to music without breaking into song, so sound patterns are often enlivening. Everybody likes playing around with sounds: babies and small children do it all the time, but often older people get too up-tight to continue. Poems can be a sort of sound playground. You can use rhymes at the end of lines, but you don't have to (ancient Greek poetry didn't rhyme, for instance, though it was rhythmical). You can also use half-rhymes, alliterative patterns, repetitions, refrains, or subtler devices within lines rather than simply at the end of them. Using some sort of sound pattern helps give the poem body.
Always ask if your poem is too long? Usually it can be shortened to give it greater impact. Don't patronize your reader by explaining everything -- give your reader a bit of room for imagination. Better to write one good short poem than a hundred long, mediocre ones.`