From clearly articulated goals to a well-argued presentation of the broader implications of your research, this is what grant reviewers are looking for:
The Art of Writing Proposals, from the Social Science Research Council
How to Win a Graduate Fellowship, from the Chronicle of Higher Education
Foundation Center’s Proposal Writing Short Course
Applying for Artistic Grants and Fellowships: Some practical suggestions learned from personal experiences, both good and bad, by Prof. Jeffrey Hass, Jacobs School of Music
The Making of a Successful Proposal, from UC Berkeley Graduate Division
Common Errors in Grant Applications, from How to Get Money for Research, by Mary Rubin