Charity Navigator is really the first place to start. They make sure that the charity is spending money on actually helping people, not on CEO bonuses and ineffective administration.
But, for stuff in other countries, you really do have to do some research. Figure out what’s going on in the region, and what you want to be done – not just, something, but specifically what. A lot of really good charities by Charity Nav’s standards are going to be NGOs of the paternalistic, White Man’s Burden variety. It’s really a lot easier to navigate not just the finances, but the politics, when it’s local or at least in the same country you live.