One little note of caution I would insert here -- the issue of vetting charities (and people who profess reluctance to give to charities) often ends up focusing on fears around "overhead". CharityWatch in particular is all about monitoring overhead.
Overhead, for those who don't know, is the expenses a non-profit has that aren't directly on programs that fulfill its purpose. For instance, non-overhead spending at a food pantry would be purchasing discounted food from a supermarket; overhead costs might be rent on the space, payment for the electricity to run the refrigerators, or paying staff to write grants or plan and throw a fundraising event.
People have a lot of feelings about charities spending on overhead, because they feel like "but I wanted my money to go to people who need help, not to buying toilet paper for the office!" Which I get on an emotional level, even if I fundamentally disagree with it. And sure, a mismanaged charity probably will spend a high proportion of its funds on overhead. But that doesn't mean that overhead is a bad thing in and of itself, and that you should base your decisions on it. It's better for non-profits to be staffed by full-time workers than by volunteers, and it's better for those workers to be adequately compensated in offices that are taken care of than for them to be living paycheck-to-paycheck and needing the assistance of other charities.