It's like anything else, you need to gather data from several sources, then cross check and verify.
Example, and I'm not slamming or axing ARRL. ARRL's repeater directory comes out annually. Everyone knows it's full of dead pairs and other errors or omissions. But hey, that's what the repeater councils are sending them to publish, so you have to crosscheck with local club websites, coordination websites, operator reports, reapeaterbook.com, and alike. Repeaterbook.com is an interesting source. They have gleaned data from every source they can find, then us end users log in and confirm whether a site/freq is up or down.
Same for air band. It's not like we were paying money to Jeppesen and getting bad charts. After all, it's a hobby.