In "real life" I work as a grant writer. At first glance there's not much that's similar between this type of writing and my fiction. Or even my nonfiction. But it HAS helped my writing.
2. Show don't tell. Even with a grant, it's important to show the reader why it's important that you receive the grant money. I usually show this by using metrics and outcomes. You can't just say "because I said so." Just as with fiction, show the reader. Make him or her believe.
3. Be brief. Don't use a page to say what you can say in a paragraph--unless you really have to. You have to engage the reader, and then keep her engaged.
4. Proofread. Do I have to say more?
5. Know your audience.This is important. If you're audience is 13-year-old girls, your language is different than if it's middle-aged suits.
6. **Update! Research -- Tracy made a great point in the comments about research so I wanted to add that to the list. It's important for fiction as well as nonfiction...and grant writing.
Amazing to me that there are any similarities in these types of writing. On the surface they feel soooo different. Thoughts? Other theories?