Iye:
Tipping: There are no set rules for tipping, however locals don't tip much. Generally in a restaurant a 5-10% tip is fair , but if the service was bad you don't have to tip. In bars people usually leave a little change. It's common to tip to the nearest euro for taxis and restaurants and a bit more if is high class.

Identity Issues: Never imply to a Barcelona native that he's from a region of Spain or that he speaks a variation of Spanish. You will very likely get berated for this. Catalans are very proud of their unique history, culture, and language so be mindful of this.

Greetings: It's typical for women to give each other, or a man to a woman and visa versa 'dos besos' two air kisses on each cheek even if they are strangers. Be aware that Spaniards tend to have a little closer personal space than Americans.

Meals: In the Mediterranean restaurants usually open around 1:30pm for lunch, and 9:30pm for dinner. If you meet up with locals for a meal expect them to be reasonable on time, but not exactly on the dot. Expect to pay just your share of the bill unless someone's invited to pay.