The Programs to Donations Ratio is the easiest and quickest way to determine whether a charity is worth a donation. The "national average" is around 7% according to what I have been hearing, meaning that for each dollar that you give, 7 cents goes to the programs that the charity supports.
This is nutz. I've set my limit at 50%, and it should be higher. If a charity is based in my state, employing fundraising organizations within the state, thus providing employment to people within the state as well as supporting their programs, I'm willing to go as low as 30%. But I've gotten charities calling me who don't give more than 5%. I give them my requirements, and invite them to call back when I can see that they meet my criteria.