Most of where I make my mechanics observations is the home games here at Western Michigan, and I learned a few things today, among them:
Please verify, but if a receiving team player makes the incomplete pass signal

on a punt return, is that the same as a fair catch? On a punt, Ball State's returner made the incomplete, "Get away" signal and then fielded the punt when it rolled his way. He ran about a yard and a half with it and got his clock cleaned. WMU player was called for a dead ball personal foul. If my memory serves me correctly, I thought it was illegal to take more than two steps, barring momentum, after securing a fair catch.
If there is no huddle, and the defense has 12 on the field, at what point do you call illegal substitution?
Is sticking your fingers inside eye opening in front of the eyes of another player's helmet considered a facemask/hands to the face? I saw that happen and it wasn't called.
On an unrelated note, the umpire in today's game has a cannon. I don't know how much the weights on the flag are, but he was throwing that thing more than 50 yards. I was impressed.