One mistake I made a few times was being too close the PA. People should try not to do that as it can be unbearably loud.
The Guiness book of world records removed the loudest band category from the book. Too many band were constantly trying to be the loudest at the audience's mercy.
One of the times it was a Black Sabbath show. My seats were front row and I was between Tony Iommi and the PA. It was so loud where I was sitting that I was cringing each time I noticed Tony about to use his volume pedal. Black Sabbath isn't known for being very loud but I learned my lesson about being too close to the PA.