While Buffy, Spike, and Angel are walking around town, gathering supplies for the spell, Buffy has a stake. Later, when confronted with the group of vampires, she is forced to break a broom for a stake because she no longer has it. At no point was it shown why she had lost the stake, suggesting that it was a script oversight.
(At around 25 mins.) Spike is holding a broken bottle to Willow's face. When the camera is facing Spike, Willow's hair is on her face. When the camera is facing Willow, her hair is to the side and switches back and forth as the camera angle changes.
When Buffy is holding Spike down, the hand that's holding his throat changes from right to left and back again during shots.
After Buffy talks to Angel about going to college, she gets up from the couch. Sarah Michelle Gellar's mark (a red X made of tape) is clearly visible on the couch cushion to let the actress know what part of the couch to sit on.
At two minutes in, as Spike crashes through the sign, the mast of the mobile lighting tower that is illuminating the scene is visible in the distance in the upper left corner of the frame.
(At 37 min.) Vampires break through a window. Buffy and Angel begin throwing bottles of holy water at them to drive them back out. As the vampires flee, the backdrop outside the window can be clearly seen changing behind them and switching from a very near vine-covered wall to a city street with several buildings now across the street from the shop.
Spike is seen disinfecting his hand burn with alcohol, but this would be unnecessary as vampires cannot be infected by any natural diseases.
It makes no sense for Xander to be surprised that Cordelia keeps pictures of him in her locker in view of how hard she is crushing on him. He has no more reasons to be self-conscious. In Dead Man's Party (1998) she was all but glued to his face and could not stop making out with him in public.