1. Never eat at a place called Moms.
2. Never buy an antenna that has the word "Miracle" in the name or
description.

Other things to avoid pertaining to antennas:

"This new principal cannot be modeled in existing programs because of their
limitations"

Claims that a particular geometry has magical properties.

E/H CFA or some other alphabet soup descriptions coupled with any of the
above.

Things to be sceptical about:

Any antenna that touts take off angle and F/B ratio as primary features.

Low SWR from DC to Daylight

Any 1/4 wave virtical that needs no radials because of some wizzbang loading
system.

Special gadgets in the feedline that makes it become a radiating element.

This by no means the extent of things to watch out for. A real education is
to read the adds for CB antennas, then when the same claims are seen for a
ham antenna put the credit card back in your wallet.

P.T. Barnum should have sold antennas. His statement would then have been
"There is a sucker born every 30 seconds"