The BBB (GIVE.org), GuideStar, and Charity Navigator are valuable sources of information about charitable organizations.
Keep in mind that just because a charity does not meet all the requirements does not necessarily mean that they are a rip-off or inefficient, but it is good to check which requirements they did not meet to see if they seem important to you.
For example, “programs vs. salaries and other overhead” may get over-emphasized. Small non-profits often look bad because, out of necessity, they must spend a larger proportion of their money on fundraising.
It’s also true that some non-profits are mismanaged at best — and scams at worst. They’re not all righteous do-gooders who are being slammed unjustly by the non-profit rating groups.