Searching and writing for grants can be a messy process so be ready. You may have to change your plan in order to find what will work.
Writing a grant is like writing a persuasive paper with intense evidence to support why the funder should give you money.
Know your organization/cause intimately.
If you are not passionate or knowledgeable about the organization/cause, why should a funder be?
Once you find a grant, make an outline of ALL of its requirements and start matching what you have and what you need in order to meet all of those requirements. And then make it SUPER CLEAR that you do indeed meet all of said requirements. Do not make the reader work for it.