Like the "Tip" above, there are many different kinds of "prompts" for storytelling. A prompt is just something that gets your mind and imagination going. You can go to a time in your life, a person, a place or a feeling. Eventually, you will get to an image; something that you will then describe to the audience as you reveal your story.
At East Valley Tellers of Tales (EVTOT) we have been doing "Improv Stories" that begin by having group members "prompt" the teller with three words that they must then incorporate somehow into their impromptu story. Some folks make up completely new stories, and some, Like Maya Jones incorporate those words into her personal stories; not an easy feat!
Back in 2006, I took a poetry class at Scottsdale CC. The teacher gave us an assignment to write a poem and incorporate eight words that she gave us. I can't find my original notes, so I don't remember all the words, except two, "blueberry" and "echo". Here is the poem I wrote.
Just below the cliff’s edge now.
Breathe in. Breathe out. Suspended,
Weaver’s Needle looms in the distance
As the desert bowl of dust
Fills the vastness below.
A soaring eagle calls out,
Like the voice inside that spurs you on.
And you can taste
The echoes of morning’s dewy blackberries.
Reading it again, now, I think perhaps I might extend it into a story...hmmm.