Many proposals fail because of loose ends. The proposals should be carefully prepared. Although misspelling, sloppy citations and the like are not a reason for declination, they certainly do not create a favorable impression. It is always important to have a number of colleagues and professors critically appraise your proposal prior to submission. The more questions you deal with in advance, the fewer that can be pointed to in a review.
Many researchers apply to a number of agencies for support of research.
You are asked to provide information regarding other proposals in process or anticipated. Should you receive funds from another source while your proposal is under consideration at NSF, please inform the program director. Should NSF then recommend an award, we will discuss other funds. We cannot provide duplicate funding, but we often do coordinate funding with other foundations and agencies. This may require you to provide a new budget prior to an award.