At the end when Ronnie is talking to Cindy on the lawnmower his sleeves go from being unrolled, to rolled, back to unrolled again.
Notice the scene where Ronald and Cindy are washing her car. The drivers side door is not closed all the way.
Near the end, during lunch at school, Ronald goes to sit at the table with the freaks and gets shunned. Later it shows a scene where there are two trays near him with Shasta cans on them. Then a minute later it shows a shot from above the table as he is leaving and there are no trays near him.
In Cindy's bedroom, when the phone rings and they go to the TV, you can see the boom mike guy when she turns off the TV. You have to pause the movie to see it and look real good.
When Ronald is in his bedroom calling Cindy saying he is Donald, you can see a hand on his foot of his bed! Look real fast, you can see it on the right side of his bed if you pause it.
At the mall, when Ronald sees Cindy returning the suede outfit, if you look carefully while Ronald is a the glass door you can see Steve Rash, the Director in the glass door on the left of Ronald's blue shirt.
In the scene at New Years Eve when Cindy is drunkenly making her way around to different rooms, the couple that 'is home for the holiday' throw a shoe. This shoe doesn't come from inside the room, instead it is thrown from behind Cindy (in the hall). If you look carefully, you'll notice the shoe coming from behind instead of from inside the room...