Continuity mistake: In the scene where Spider-Man is being given the key to the city, the view as the camera sweeps the band, it shows a full row of members on the top left, but when you see the band from the park angle (during MJ's conversation), there are less band members.
Continuity mistake: Before Sandman is turned into sand, the craw-like machine lifts up tons of sand but it never gets in his eyes nor sticks to his shirt.
Continuity mistake: When Peter gets Eddie out from Venom you see a lot of symbiote stays on his chest after he finally gets out from it, but in the front shot of the symbiote you see no remnants on his chest.
Continuity mistake: In the scene just before Mary Jane throws a hollow brick onto Eddie's head, his back is briefly shown where we can see that he is not wearing any dress under his venom suit. But later at the end when Spider-man tries to save Eddie by pulling him out, his dress comes back on him.
Chosen answer: Answered in the comics: Peter's Spider-Sense tells him if someone is looking when he's about to enter/exit the apartment as Spider-Man.
Captain Defenestrator