Don't do the famous Ramblas: over-rated, over-crowded, tacky, lined with caged birds and tourists trapped in low-grade restaurants.
Do stroll down the Rambla de Catalunya, Barcelona’s most elegant boulevard. If you’re heading north, pause to observe the church perched on the mountain overlooking the city. It’s immodestly named Tibidabo, the Latin for "I shall give to you"—Satan’s words to Christ when he sought to tempt him with all the Earth’s glories.
Do go and see Gaudi’s Sagrada Familia church, the longest architectural work-in-progress, half medieval Gothic, half Star Wars—and get there early, as the queues can be damaging to your health in the blazing summer sun and destructive of your soul at any time of the year.
Do get lost in the Born, near the sea in the old medieval part of the city: loads of hole-in-the-wall bars and funny little shops run by grumpy old-timers, plus the austerely stunning 14th-century church of Santa María del Mar. The Hotel Banys Orientals, with double rooms from €100, is sleek and affordable.
Don't miss La Boquería, possibly Europe’s best food market. Choose your pata negra ham, stop for lunch, or just go for a wander. In terms of visual feasts, it beats even the Picasso Museum. But don’t go on a Monday because you’ll miss the fish, the lobsters and the goose barnacles.
Don't stray north of Diagonal Avenue, as there is nothing to see that is distinctively Barcelona-ish, except maybe in the Bohemian barrio of Gracia, where real people live and tourists rarely venture.
Do eat top-drawer tapas at Ciudad Condal or its sister restaurant, Cervecería Catalana, preferably outside. If you arrive after 8.30pm, while away the inevitable wait by feasting your eyes on the glistening range of treats displayed at the barra.
Don't bother sampling the grub at the various failed El Bulli clones. Pretentious, expensive (the Spanish crisis is for real) and, frankly, a bit dated now.
Do visit Barcelona FC’s stadium, Camp Nou, which is awe-inspiringly massive and has a museum full of touch-screen displays. But don’t wear the Spanish national-team shirt, even if most of the 2010 World Cup-winning side played for Barça. Catalan nationalist sensitivities must be respected at all times.
Do linger over dinner if you are planning to make a night of it. No self-respecting club gets going until midnight, and usually not till two in the morning on weekends. A good option, especially for balmy nights, is a drink on one of the hotel rooftop terraces, such as the Condes de Barcelona, the Majestic or Casa Fuster.
Do go to Sitges—better beaches than in Barcelona and only half an hour away by a train that offers sea views and classical music. It’s a charming, cosmopolitan, little big town that is also the gay capital of the western Mediterranean. No need for heterosexuals to feel out of place, though. As the Englishman Bobby Robson, a former Barcelona coach, put it: "Don’t worry. There’s plenty of crumpet too."
Don't call Barcelona "Barça". It’s the name of the team, not the city.