Ann has written many articles to help the writer.  Read some of them here.

The Balancing Act of Pacing: Mixing Dialogue, Action, Thoughts and Narrative

Changing Plot in Mid-Stream

Getting to Know You (download a copy in Microsoft Word)
The key to selling is to hone the craft of writing.  One of the last things you'll do before you sell is learn how to create believable, memorable characters and convey their thoughts and feelings on the page.  There are many ways to develop believable characters.  One is to complete a character sketch.  This one is a good start, but you'll want to add to it as you go, and delete those things you don't use.

Make Every Scene Count

What's a Ticking Clock and Why Do I Need One?