Think Small and Specific. Focus on the details and let the big issues take care of themselves. Writing about trees in The Piano is more likely to generate something original than writing about true love in The Princess Bride. Don't expect to have something brilliant to say the instant you sit down at a computer. You need to take time to think, to plan, and most importantly, to write.
Nothing generates ideas better than writing.
The ideas won't come, or if they do, they won't work after the first few paragraphs. Do not assume that you will start with a master vision that will execute itself perfectly on paper and emerge fully intact 750 words later. Develop an Intolerance for the Uninteresting and Insincere. Learn to recognize the moments where you don't mean what you say, but are saying it anyway just to complete the structure of your argument. Remember that what bores you is even less interesting to your reader.