In an open call for proposals where a donor invites applications from many NGOs, it may be difficult to seek inputs. Since such calls are competitive, the donor often does not want to favor any single NGO by providing feedback on the proposal. In these cases, the best strategy is to carefully review proposal guidelines, donor priorities and objectives, previously funded projects and other details. This research can provide organizations with the information needed to develop a competitive proposal.
If approaching a donor directly, then it is a good idea to try and discuss project ideas before submitting a full proposal. It will be difficult, almost impossible to approach big foundations, but the new generation of donors might give you time. Heads up! The input from donors might be more of a critic. It on you how you use the criticisms to better your project and proposal. It is important to think about how your project or program fits into the donor priorities. The donor may provide reference material, such as previously funded project documents, which can be used to create a more customized proposal.