I keep in mind: Charity begins at home.
I take care of my family's needs first and foremost. I then ONLY do charity where I feel like... which is usually NOT when I've been asked to.
The one year my son was in public school not a SINGLE week went by without them asking for money. Not a week! Some weeks we had multiple requests. They were mostly "fundraisers" to which the school got a whopping 5%. So I out and out refused except for the cookie dough sale (the one time the kids had flyers and schtuff). Instead I gave $50 to my son's teacher for school supplies (not a lot, but better that the $2.50 that would have gone to the school... much less his own teacher, and we were living off of student loans at the time). I also donated several items (like a centrifuge) to the science dept, and would get others to help get money together (or work hours together) specifically to go to the school. Not 95% to whatever company and 5% to the school.
Ditto... I happen to have more time than money... so something kiddo and I do most years is a babyfood & formula drive one or three times a year for the local battered women's shelter, or to my OB/Gyn office (who take a lot of pro bono/ low income patients), or to be distributed through kinship placement fostercare. When in doubt I often phone up Catholic Community Services. We're not catholic, but it's an org that has helped more people that I know personally than any other. And the vast majority of it's "employees" are volunteers. So if I happen to have some time or need some ideas for barter work (like who needs formula, or jackets, or PJs desperately right now?), I can usually phone them up and find out who "needs" that's not getting.
I'll also donate actual cash to the Red Cross, Doctors without Borders, or other NGOs that I particularly happen to like. Since I listen to NPR I pledge some there as well. I don't care how big any of their overheads are.. their overhead allows them to help millions.
We don't happen to have a lot of money at this point in our lives. Often, over the first 5 years of kiddo's life people would be hounding me to donate to organizations that I was a RECIPIENT from. (Ummm... Sorry.) But when we have a little extra I like to cast bread upon the waters. But it has to be at a time of my own choosing, and at my own discretion. I'm far more likely to give a bum a dollar (who am I to say their pain isn't worth dulling?), or buy a homeless kid a burger, than I am to give to any organization that I don't have their annual reports in front of me.