If your charity is collaborating on a program with another charity or business, include with your proposal a letter of understanding between your charity and the collaborator stating the roles you will each play in the program, or at least obtain a letter of support stating that the other charity endorses your applying for the grant.

If your charity has been (favorably) in the news, by all means include quotes from articles or in some cases the entire article, as additional confirmation that yours is a legitimate charity worthy of support. When your charity appears in the news is a great time to submit proposals because the funder might already be thinking about you.