1. Find a prose passage that seems poetic. You know you read some stuff that just sounds cool.
2. Break it up into more poetic lines and stanzas. Reformat it, basically.
3. Alter it to better fit your definition of poetry. A few options: even out rhyme, meter; more flowery words; clearer images.
I used a passage from Cutting for Stone by Abraham Verghese, which I copied below the poem. I loved reading that book. It's about a pair of twins born in Ethiopia, Shiva and Marion. Their parents were an Indian nun (who died in labor) and an English surgeon (who fled shortly after their birth). They were raised by two Indian doctors at a mission hospital. Very interesting story about love, medicine and family both chosen and natural.
Death of a Twin
His body was warm.
He never took a breath
His expression never changed.
I felt his pulse,
regular for a full minute.
Then it paused,
as if the heart had just realized
the lungs had quit.
With a final throb, he was gone.
Of all the pulse types,
this was both the rarest
and the most common.
Every pulse possesses
the potential to be absent.
I closed my eyes and cradled him,
his skull buttressed against mine.
I felt physically vulnerable
lying here next to him
in a way I hadn't known
when we were a continent apart.
With his death
my biology was altered.
The heat was rapidly leaving his body.
I lay there, my head against Shiva's, a finger resting on his carotid pulse. His body was warm. He never took a breath after the tube came out. His facial expression never changed. His pulse stayed regular for almost a minute, then it paused, as if it had just realized its lifelong partner-the lungs-had quit. His heart sped up, became faint, and then, with a final throb under my fingers, it was gone. I thought of Ghosh. Of all the pulse types, this was both the rarest and the most common, a Janus quality that every pulse possesses: the potential to be absent.
I closed my eyes and clung to Shiva. I cradled him, his skull buttressed against mine and now wet with my tears. I felt physically vulnerable in a way I'd never felt when we were a continent apart, as if with his death my own biology was now altered. The heat was rapidly leaving his body.
Cutting for Stone by Abraham Verghese