Define what your nonprofit blog must accomplish
A nonprofit blog serves different goals than a commercial one. Before writing a single post, define explicitly what the blog must do: attract new donors (content that demonstrates mission impact and urgency), engage existing supporters (updates, impact stories, and volunteer spotlights that build loyalty), educate the public about the cause (accessible explanations of complex issues), or recruit volunteers and staff (behind-the-scenes content that conveys culture and purpose).
Most nonprofit blogs try to serve all of these at once and serve none well. Start with the single most valuable goal and design the blog around it.