Watch your pockets in the city’s tourist hotspots. Many an oblivious soul has lost bags or wallets to the crafty thieves of Las Ramblas.
Though almost every local is a fluent Spanish speaker (and many know English, too) learning a few phrases of Catalan will endear you to shopkeepers, waiters, and any other proud Barcelonans you encounter.
Tipping is something that you can do, but you do not have to. If you opt to tip rounding up to the nearest euro or 10% is sufficient.