Simplistic, naive design, broken plant stems, low to zero symbolic content, no ground or atmospheric ionization, no magnetic effects in the soil's metallic particles
-- Dead give aways of the fakes
BTW: "fake" means done by Humans, of course, "Boyz with Boards and Ropes" -- pitiful
In real crop circles, the stems are not broken, but are bent, some inches
above the ground. The plants are still alive and continue to grow.
Also, there are usually ionization effects that can be measured over the
area of a genuine crop circle, at least for a while after its creation, often
minor magnetic effects measurable through the ground.