Proofread every carefully prior to submission, keeping in mind that the application documentation is the only thing that will be considered in determining whether or not funds are awarded to your cause.
Ask someone else to proofread the document for you, just to be sure that you didn't overlook anything that needs to be corrected or adjusted.
Carefully edit and proofread your resume.
Be sure to provide all of the requested information and proofread it carefully before turning it in.
Make sure to proofread your letter to ensure there are no mistakes.