The kid talking to Ashley at the party mentions that he got 50 bonus points for his use of the word "mazer" in Scrabble. 50 bonus points are awarded only when a player uses all of their letter tiles in a turn. You have 7 letter tiles per turn, so there is no way he could have received the 50 points under the rules of Scrabble.
When Shaun leaves the Frat party and starts to walk around the campus his hair is messed up. Then he meets Professor Skinner and his hair is neat and parted in the middle. After speaking with the professor about his writing he leaves and his hair is messed again.
When Ashley confronts Tanya about not helping Shaun get in to Stanford Ashley's left hand is placed on her hip. In the next shot, her left arm is down at her side and she now has her right hand on her hip.
When Don Durkett moves to get close to Shaun while Shaun is seated on the couch, Ashley is on Shaun's right. When the shot switches to show the shot over Shaun's shoulder, Ashley is on his left. The next shot, she's back on his right.
When Bud leaves the house to discuss getting a divorce with Krista, there is only one car parked at the house, a Nissan Pathfinder (Shaun's car). There is no car belonging to Bud parked in or around the house. Bud mentions he drives past the house on his way home from work. But where is the car, and how did he get there?
Cindy wheels Bob out of the house onto the front stoop just before he falls down the front stairs. She is clearly visible beside his chair as he begins to roll. When he hits the car and the camera points towards the front stoop, Ashley is seen standing and watching but Cindy is not on there.
While at the Dean's house, Ashley asks Shaun about his brother's aspirin (drugs) and Shaun reacts shocked and nervous as if he somehow already knew she gave some to the Dean, but he was out in the car obtaining his transcript when she did that - so obviously he would not have known.
At the end of the film when Shaun and his friends are on the beach, he decides to take up surfing again. Shaun and his friends pick up their surf boards and run towards the water. However, the sun is setting and the sea is really calm. There are no waves at all, not even a ripple.