The first page of your novel (or story) is crucial. If an editor or agent isn’t interested by the first page, then chances are they won’t read any further.
Novelist and writing instructor Peter Selgin (author of 179 Ways to Save a Novel and By Cunning & Craft) decided to address this very topic by starting a blog titled Your First Page that helps writers with the first page of their work. Writers can submit their first pages and receive feedback (first from Selgin himself and then from other writers).
Getting objective feedback is one of the most important things you can do improve your manuscript. Selgin’s blog is a great way to get started. Some other ideas include joining/starting a writing group (Becky Levine’s excellent book The Writing & Critique Group Survival Guide has some great insights into how to go about this); or check out WD’s peer critique studio.