Before you go
ESTA: apply online at least 72 hours before the flight. It lasts two years.
Getting around: tap a contactless card or phone at the subway gate. Rides are free after 12 in a week.
Tipping: 18 to 20% in restaurants and taxis. It isn't added to the bill.
Weather: mid April is usually 10 to 18°C. Bring a light jacket and comfortable shoes.