The story begins "in medias res" ("in the middle of things"), with Shane running into the school bus and having great difficulty closing the door against the oncoming walkers. When the scene is shown again, this time Shane runs into the bus well ahead of the walkers and closes the door easily.
In the kitchen scenes where Lori and Andrea are discussing Beth's attempted suicide, through the window you can clearly see it is heavily snowing although this episode takes place in the summer.
As Rick and Shane are driving away from the farm to drop off Randall, Shane sees a lone walker crossing the field. As Shane and Rick are driving Randall back to the farm, Shane sees the same Walker walking across the field, but he is on the other side of the road, so either the Walker has crossed the road and is walking back or it should be a different Walker.
Shane uses his knife to cut his hand a short time after stabbing a zombie in the head. If the zombie pathogen can be transferred by a bite or scratch then using a knife to cut yourself after using it on zombies would be very risky. Even if this doesn't transfer the disease there would be no way to be sure of this.
When the zombie crashes through the window and Rick stabs it in the head, you can see the retractable blade of the fake knife caught halfway in the handle.
After Rick runs out of ammunition his gun can be heard dry firing but the hammer isn't moving.
At 22 minutes 12 seconds in, as Rick tackles Shane to prevent him shooting Randall, Andrew Lincoln's (Rick's) ear mic comes loose from his left ear and briefly flaps about as he throws Shane to the ground.