The demarcation between science and pseudoscience is a fuzzy line. Science vs. pseudoscience is a false dichotomy, like religion vs. cult, where there is a spectrum between the two. Pseudoscience has one or more of the following features:
Hostility towards scientific criticism
Science requires criticism. Bad ideas and methods get knocked down. Pseudoscientists can feel picked on by such criticism and cry conspiracy. Science provides a system for validating ideas and forces disconfirmation of wrong beliefs.
Ignorance is a virtue
Pseudoscientists can fancy themselves as being untainted by the scientific community and therefore able to think outside the box. Science thrives on creative thinking for problem solving and testing hypotheses to best explain existing data.
Start with a conclusion and work backwards
Pseudoscientists can start with a "theory" and then retrofit or cherry pick evidence to fit the conclusion that they
want. Creationists are a good example of this pseudoscience feature. Scientists modify or discard theories based on new evidence, granted that the process can be slow.
Pseudoscientists can use jargon to dazzle and obfuscate instead of illuminate. Scientists use jargon to increase precision and
remove ambiguity. Scientologists are a good example of this pseudoscience feature.
Shift the burden of proof
Pseudoscientists can shift the burden of proof away from themselves and challenge others for disproof. But the burden
of proof is on the claimant. And the more extraordinary the claim, the higher the bar of evidence.
Failure to consider all hypotheses
Pseudoscientists can prefer sensational hypotheses over more likely mundane ones, and they can even propose whole new laws of
physics to explain phenomena instead of considering existing ones.
Reliance on anecdotes
Pseudoscientists can rely heavily on personal testimonies and anecdotes rather than well-documented studies. This is especially
the case with health and medicine. And it's a red flag when fundemental principles are based on a single case, such as with
chiropractic and iridology.
Scientists count the misses, not just the hits; this is demonstrated by a
TED Talk by Michael Shermer.
Simple solutions to complex problems
Pseudoscientific solutions can range from a universal theory of everything to a single medicine, procedure or product that cures all ills. As to why such simple solutions have been overlooked all this time can be attributed to grand conspiracies.