2. Don't Block Pavements

This is a particular bugbear among everyone I know in Barcelona. It takes ages to get through the city center because of the crowds of tourists blocking the streets and dragging their suitcases around. Do look where you're going and if you stop to take a photo ensure that you are not stopping people from getting past. You may be on vacation, but locals have to get to work, do their shopping and pick their kids up from school.