- Has the most effect on QALY (quality-adjusted life year) per dollar. https://en.wikipedia.org/wiki/Quality-adjusted_life_year
- Whether the organization can effectively handle money given to it (i.e. it actually can quickly scale use of it - UBI-esque things like GiveDirectly seemingly fall on the higher end of scalability but effectiveness may still be up for debate)
- Givewell (when one donates to them for the discretionary grantmaking option) tries to allocate money for grants over time for what they see as the most effective grant based on their research / current needs of the organizations seeking funding. See https://www.givewell.org/about/FAQ/discretionary-grantmaking for more info. Also intriguing is their 2018 giving spreadsheet: https://docs.google.com/spreadsheets/d/1EM0CCg9tvCCtEoY-QVAi...
This is my personal (and verry rough) take, honestly recommend reading the book - your local library probably has a copy in digital/audiobook formats. The book generally recommends against donating to disaster relief comparing the 2011 Japan earthquake to Haiti, though the point in that advice was largely that disasters in developed countries tend to attract more noise/news coverage than ones in other areas of the world.
If you're really lazy and just want to listen to some music in this vein, try https://lostboyevsky.bandcamp.com/album/existential-risk