Diction is the choice of words. Syntax is the arrangement of words. (Now I'm showing off but humor me. My MFA degree in fiction has put me in debt for the rest of my life so I ask for your understanding. Shall we continue?)
After getting words down on paper then begins the process of revision. Depending on what the story is about and how it's to be told, go over this first draft (right after writing it or later) and take out words or add words that will get across to the reader not only what is happening in the story but the feel of what is happening.
Also, arrange the words left on the page in the best order to get the maximum effect.
How important are diction and syntax? The words chosen and the order the words are in will alert the reader to how he or she should feel toward the characters in the story and how to feel about what is happening to the characters; and it will alert the reader to how the writer feels toward the story, too. All this without any direct instructions from the writer.
And not having instructions from the writer is a good thing because the story should not be about the writer. The story should be about the characters. The writer should leave the characters alone. Let the characters "act out" the story without the writer sticking his or her nose in. Give the characters free will even if the writer knows how it's all going to turn out in the end.
i think it's a good write and helpful for writers. would be nice if you'd insert an example of both diction and syntax. on line 9 you have choosen vs. chosen. thanks a lot for sharing. hope you write some more.