The biggest mistake is treating Milan as just a stopover. It's well worth time for art, architecture, fashion and food.
- Staying around Piazza del Duomo and missing Brera, Navigli, Isola and hidden gems such as Villa Necchi and the Cimitero Monumentale.
- Taking taxis for short trips instead of the metro or trams. If possible, fly into Linate, the closest of the three airports, and take public transport.
- Eating at tourist-trap restaurants. Look for trattorias and osterias in Brera and Navigli, and don't skip markets such as the Brera market or the Navigli antiques market.
- Skipping a day trip to Lake Como, even though the train from Milan is easy.
- Not packing for weather that is cooler and wetter than Rome or Naples (especially in spring and autumn), and wearing shoes unsuited to cobblestones.