I found and absolutely brilliant article about storytelling aimed at novice storytellers today, the article was well written and gives lots of tips on how to develop storytelling skills.
The article listed characteristics of a good story as follows:
* A single theme, clearly defined
* A well developed plot
* Style: vivid word pictures, pleasing sounds and rhythm
* Characterization
* Faithful to source
* Dramatic appeal
* Appropriateness to listeners
If you are beginner storyteller looking for material and resources to help develop your storytelling skill, I strongly suggest you read the full article, be found here