Up until the end of the movie Angelina Jolie doesn't have her dragon tattoo on her left arm. When all the couples meet for their parents to renew their vows you can then see that she has a red saran wrap heart on her left arm.
Throughout the entire movie, whenever there is a scene (and there are many) involving martinis, between shots the olives and level of vodka in the glass change. This happens many time when a character either eats an olive or is about to eat one, it will re-appear in the glass seconds later. Also - many times where the character is starting to say something, and the view is changed to be from their point of view and their lips are no longer moving.