If you go here Casino Affiliate Programs to look at the list of programs, some have a “certified” icon. These have been voted good by us affiliates. I think there may be a list of just them someplace but I don’t know where…
You also need to go to all the program forums here in the forum section of the site below and click on the one you are considering and see if issues have been resolved.
When you want to add one to your site, you can also make a post here and ask us and people will tell you about their experiences.