Your first 1,000 words must compel an editor or agent past the milestone where she would normally reject a manuscript. The deeper you can force a publishing professional to read into your novel, the greater the likelihood she will eventually be interested enough to buy or represent it.
Here are a few pointers on how to make your first 1,000 words work:
Introduce the heroic character and give clear signals about his personality, appearance, flaws and strengths. Force your reader to care about this character.
Introduce, or at least allude to, the heroic character's worthy adversary. Characterize her as well.
Present or strongly suggest the surpassing conflicts of the story. You may have several—you should have several—but certainly the most important should come into play early in the story.
Deliver evidence of the danger, suspense or dramatic irony you might have hinted at in the first 100 words.
Foreshadow crucial scenes to come in the first 50 to 100 pages to the point-of-no-return complication.