When Bella decides to try some blood for the first time you see Jacob move over away from Bella. But when Edward returns with a cup of the blood you see Jacob move away from Bella again.
Jacob moves away the first time, he then moves farther away the second time.
Edward and Bella left their wedding reception at night in Forks. They arrive in Rio wearing the same clothes, at night. Forks' time zone is 6 hours behind Rio. Even assuming they left as soon as it got dark and flew in the private jet, they would have arrived in Rio when it was daytime.
When Bella walks up to the altar during the wedding, she is holding her bouquet in front of her. In the next shot, she is not holding the bouquet any more. Alice, as her maid of honor, is never shown holding the bouquet, either.
Before suggesting that Bella should drink blood, Jacob gets closer to Bella to keep her warm, the camera focuses on Bella's and Jacob's hand and Bella has her engagement ring in her right hand, but in the next shot that focuses on their hands again, the ring is gone. Then when Bella begins to throw up, the ring is back in her finger.
In the indoor chess game, Edward has a passed pawn on g3 - despite Bella retaining her pawn on g5 - making the position highly dubious as to get there it would have been necessary to have somehow jumped over the g pawn, an illegal move.
It is often thought that the moon is full every night during this movie. This is not the case. The moon is full and visible on only two nights during the film - on the night of Edward and Bella's wedding (the first night of their honeymoon) and after Edward and Bella have returned to Forks. The reason for this is that exactly 28 days have passed between those two nights, thus the moon has completed one full cycle. The full moon is shown during these two nights to alert the viewer that Bella's pregnancy has progressed to nearly full-term, even though only 28 days have passed since conception.
Although Edward and Bella clearly get married during the daytime, none of the vampires sparkle because Forks is usually cloudy weather and only direct sunlight causes their skin to react. They regularly attend school and work etc during the daytime without sparkling.
The goof item below may give away important plot points.
When Bella first decides to drink human blood in order to save herself and her baby, she says the words: "I'll try anything." If you look closely at her mouth when she says these words, you can see that even prior to taking her first sip of blood, there is a red, bloody substance between her teeth.