When using Gmail I have a bunch of filters that make it easier to read through my spam mail.

For instance: IF X email is in the spam folder AND contains any of the words (Cialis, Viagra, Rolex, etc...) -> Move it immediately to the trash.

This cuts down the number of emails that stay in my spam folder by a huge margin, and makes it much easier to check for false positives.

That being said, I no longer even bother checking. I've been with Gmail for 5 years and I've never had a false positive.