writing the poems...

How do you guys start writing your poems? When Theo gives us guidelines for a poem in class or as an assignment, I feel like I write a beginning line of five different poems each time, then pick the one that I like best. I do not have a problem thinking of a subject or some theme to write about, but I can never seem to actually write about it - I can't get the words on paper. In class sometimes I will write a line that I think could make an interesting poem, but then later I don't know where to go with it. I think my problem is that I try to tell a story. It's instinct. Looking back at my poems, they are all stories. But poems aren't stories, are they? I think Mr. Moss would say "no."
This gives me a new respect for poets. it shows that some people just have a mind for poetry. All my stuff starts and ends in the same place. Regardless of how I feel about the person, I would be open to any comment by a published poet. Stan Moss, for example, didn't strike me as the most reliable of sources regarding world history or his own history for that matter, but his work speaks for itself.