I've used Charity navigator for years. They have alway been a very good source of high-quality charities to ensure the bulk of the donation goes to the actual cause. It even has audit information breaking down the distribution of funds. Givewell is another recommendation.
+1 Management vs advertising vs program spending can drastically vary from charity to charity. And there are some bad practices even by very well-known names (see: ad spend).
https://www.charitynavigator.org
https://www.givewell.org/