The biggest mistake I see is lifters doing "the big three" with absolutely horrible form. Knees in on skwats, elbows straight out at the bottom of the bench stroke, rounded back on deads. Stuff like that can lead to injuries in a hurry. Some of it is due to trying to lift more weight than they are capable of, but most of the time, their form is horrible to start with. I cannot slight someone for going for a max weight in any lift, but use good form.
"I can't wait 'til tomorrow, 'cause I get stronger every day!"