When they discover the girls hiding in the bathroom, we see George removing his football helmet. However, in the following over-his-shoulder shot, we can clearly see he still has the helmet on.
At the start of movie, the "tryouts" sign board put in front of judges tables changes its position from the corner table to the center one, all by itself.
After the group meets up with the coach and arm themselves, they all get into an original Hummer 1. However, when they are shown after the next scene, they are in a H2 Hummer.
In the later moments of the scene in which the teens are gearing up at Coach's place, George turns around and sees Jules wearing a football helmet, which he talks him into giving him. But, only a moment before, you can clearly see George in the background already wearing the helmet.
While she's killing zombies at the funeral home there is a lot of blood splatter on Gwen's face, then when in the back of the hearse there is no blood on Gwen's face. The blood is back on her face when she arrives at the coach garage.