Entry
A Cuban embassy can tell you which visa rules apply to your passport. The paper tourist card is gone, replaced by an electronic visa (e-Visa); the embassy can explain how it works for you and what it costs. On top of this, the online D'Viajeros form, which covers health, customs and immigration, has to be completed up to 7 days before arrival, and its QR code must be shown. Medical insurance covering Cuba is required, and so is a return ticket, while the passport should have 6 months of validity. Because rules change often, check every point with the embassy and the airline.
Culture and practical - take note
Cubans come across as warm and musical, and they are curious about visitors. Avoid criticising the government or photographing the military or police. Cash matters most: bank cards issued abroad often fail to work, so bring plenty of cash in a major currency, then find out how to change it, as rates at banks differ from those on the street, and only official exchange offices should be used. Limited internet, fuel shortages and power cuts are common. Hurricane season lasts roughly from June to November. 'Casas particulares' (private homes) are a popular place to stay and offer good insight into local life. Pack snacks, toiletries and basic medicines, because shops can run short of them. Small bills are best for tipping. Finding halal food is hard.