I second Wander and olorwen's advice. My school has a grant-writing class specifically geared toward NSF, which makes mention of all of these things.
Another point I wanted to add is the use of empty space. I know it seems paradoxical to cut parts of your proposal so that you can put a line in between paragraphs or in between sections, but it really improves readability. Considering how many of these proposals each reviewer has to read, they are bound to skim over some of them. Anything you can do to make sure yours is more likely to be read will help in the long run.