No credit cards are accepted from U.S banks. Safes are in most hotel rooms. Major point - always carry toilet paper. Bring lots of film. We prefer ASA 200 for snapshots.
Bottled water is available in the stores in each hotel and in markets.
Clothing - Carry a light jacket for evenings. Men seldom, if ever, need a sport jacket as dressing is very casual. Neither men nor women are often seen on the streets of Havana in shorts except during the heat of summer, but shorts are common in other areas all year. Air conditioning can be a problem. Women do wear pants to synagogue in Cuba.