Experienced the development and production of over 50-60 films getting made each year. All very very different. Perserverance is what paid off in most cases. Sticking with a project is key. You have to really want to tell this story really badly on screen.
Passion does make a difference and being able to accept rejection.
Sundance focuses on writing which comes from personal vision. Make sure to submit your best possible version of a script. I optioned a novel three years ago, EVA LUNA by Isabelle Allende, and I plan to stay with project as long as necessary to get it developed and produced. The biggest issue in film world is distribution. Glut of product and not enough indie distributors, so times are tough.