Level 6
I usually just test it on a site that I'm familiar with.

Things to lookout for:

Do your ad block settings...
  • Interfere with video playback? Sometimes embedded videos (that are not ads) can be blocked unintentionally.
  • Block comment sections? I like reading comments/discussions on articles so I make sure the comment systems aren't blocked. The Disqus comments system is a common example that might be blocked with some ad block filters (especially those geared towards blocking social media sites like Facebook comments or Twitter replies).
  • Interfere with drop down menus or widgets on the site? Depending on how the site is made, some areas of the site may not be functional.
There are some sites that claim they test if your ad block is working properly. However, I've found them to not be reliable.
It's best to just test on sites that you usually browse/are familiar with because you know what the site looked originally and will be able to notice any changes.