Cory Doctorow joins the chorus of praise for Kate Wilhelm’s Storyteller (must read!); I suggest you check out his take. He excerpts some practical advice from the book which I now unashamedly steal for here:
When beginning a story, do not:
* Let your viewpoint wander
* Confuse immediate setting with background and let your camera eye wander in, out, and about randomly
* Start with a lecture in anything — history, physics, biology — anything. Expository lumps anywhere are to be avoided if possible, but they are deadly in the opening.
* Start in the middle of a scene. This is why flashback openings are a mistake almost every time. You interrupt an ongoing scene to tell us something that happened earlier that results in ongoing scene. Once started, the scenes should be concluded before you move on. An ongoing conversation is hard to catch up with. Who are these speakers, what is their relationship, what kind of voice should I be hearing in my head? Introduce them before they open their mouths.
* Mislead the reader with false information or try to create suspense or arouse curiosity by withholding necessary information. What you arouse is mistrust and annoyance.
* Sprinkle around neologisms or made-up words that cannot be found in a dictionary.
* Use words that only you and a few other people in your speciaility can understand.
* Use contractions if you can avoid them, and only sparingly no matter what.
* Have your character look into a mirror or other reflective surface in order to work in a description of her.
* Let your character talk to an animal or inanimate object in order to give information to your reader about what is going on.
* Play games with the sex of your character.
Related Link: Small Beer also has a page of "Memories and Lessons Learned at the Clarion Writer’s Workshop" from Doctorow, Jeff Ford, Gordon Van Gelder, Jim Sallis, Kit Reed, Greg Frost and Nancy Kress. Check it out.