Remember that it takes a lot of skill to run a national organization. It's similar to running a business. Of course, some people who run charitable organizations choose to do it for little or no pay. You'll need to decide for yourself if the salaries seem excessive. There are other clues that a charity might be less than honest.
Common sense applies.
Organizations that are ethical are willing to wait and won't push you to make a decision. They're willing to have you look at their records because they have nothing to hide. Don't give cash to charities. A check made out to the organization is much more likely to reach it's goal. Only give your credit card number to charities that you've worked with in the past and that have earned your trust.