During the "Date Dash", the pledges are told they have to grab a date, with no change in clothing, no hair fixing, and no makeup. Yet, in the restaurant, Sydney is clearly wearing white eyeliner/shadow and lipstick.
If you look closely, you see that Sydney's bangs change in length. The bangs in the front of her face are longer than the ones in back at the beginning of the movie, then switch so that they are shorter.
At the end of the movie when the repairs are being made to the Vortex, construction worker Big Ron can be seen climbing a ladder in the back ground carrying a stack of roofing shingles. A couple of scenes later, Big Ron is carrying the same stack of shingles up the ladder.
When Katy tells Rachel about Sydney White at the Rush Party, she says the word "Legacy" is three words when it is really three syllables. Kappa members are, for the most part, portrayed as stereotypical preppy blondes. Katy should not be expected to be very smart.
While the character of Sydney is brunette like Snow White, both of her parents are blond. This is genetically impossible. Yet, many of the members of the sorority dyed their hair blond, so her mother may have done the same.
When Sydney is getting on the bus to leave for college, the US flag is on the bus by the door, but is displayed backwards, with the union (the stars) on the right instead of the left. It stays this way throughout the whole scene. When the US flag is displayed with the union on the right, it symbolizes forward motion. If the bus carried a real flag on a mast instead of just a sticker, the union would be on the right as the bus moved forward because the union side is attached to the mast.
The goof item below may give away important plot points.
Since Sydney's airport card on her laptop was turned off and she had no network cable plugged into her laptop, it could not be possible for the hacker to hack into her laptop and wipe out her hard drive.