Research thoroughly the grant for which you are applying. Whether you are applying for a graduate fellowship through your university or an external fellowship through an organization that is related to your work, each fellowship has not only requirements, but a specific mission. Align your proposal to the mission and vision of the grants for which you are applying. This will give your proposal an edge.
Write a mission statement or statement of purpose for the work you are seeking to fund. Ask yourself why your work is important, how it will enrich your field of study and how it will contribute to society. Answer these questions as you shape your ideas into a concise but elegant statement.
Consider what about your work makes it singular and different from the work of other individuals in your field. Provide concrete examples of why your work is valuable and individualistic. Fellowship providers want to believe their money is helping you to break ground and enrich society. Make them believe this.
Take time to write the grant well. Plan writing time into your daily schedule so that it doesn't get pushed to the side. Writing a fellowship proposal requires acute attention to detail.
Edit your proposal several times. Read it out loud to catch any mistakes your eyes might miss. Ask a friend to read it to confirm that it is clear and fluid.