Continuity mistake: When Jax and his crew meet up with a Hispanic gang to sell them guns and are outnumbered, they run in the station wagon. The run the station wagon through a gate and roll it, destroying the front end, but magically the station wagon's front end appears with little damage afterwards.
Character mistake: Tig gets bit on the right butt cheek. Tara tells Chibs to give him a local, which is a numbing injection so she can stitch him up. Problem is that Chibs does the injection in the left butt cheek. You are supposed to give the injection close to the wound to numb it before stitches.
Deliberate mistake: When Tara is talking to Gemma in the parking lot of Stockton Prison, the chrome bumper of Tara's SUV is blurred out, probably to cover up visible crew and equipment. It looks unnatural, since the image is sharp enough that you can see the radiator itself behind the grille, and the numberplate is perfectly sharp.
Factual error: When the fat insurance guy wakes up from being drugged, he bites Tig on the butt. There's no way a person can bite through a pair of jeans. It shows the wound and there's a tear in them and blood. It looks as though a dog bit him, not a person.