1. The discoverer pitches the claim directly to the media.
2. The discoverer says that a powerful establishment is trying to suppress his or her work.
3. The scientific effect involved is always at the very limit of detection.
4. Evidence for a discovery is anecdotal.
5. The discoverer says a belief is credible because it has endured for centuries.
6. The discoverer has worked in isolation.
7. The discoverer must propose new laws of nature to explain an observation.
The list of warning signs is pretty good. The only thing that I can think to add is that the claimant relies on authority over data for their claim. Otherwise, I can think of nothing to add – but perhaps you can, and that’s what the comments section is for.
I especially like the explanation for #5:
5. The discoverer says a belief is credible because it has endured for centuries. There is a persistent myth that hundreds or even thousands of years ago, long before anyone knew that blood circulates throughout the body, or that germs cause disease, our ancestors possessed miraculous remedies that modern science cannot understand. Much of what is termed "alternative medicine" is part of that myth.
Anyway, check it out, it’s well worth reading and keeping in mind when you hear a claim made.