IMPORTANT: a special Cuban A-1 visa is required for visitors using passports from these countries: Afghanistan, Bangladesh, Cameroon, Eritrea, Ethiopia, Ghana, Guinea, India, Iraq, Iran, Kenya, Nepal, Nigeria, Pakistan, Philippines, Sierra Leone, Somalia, Sri Lanka, Syria, Yemen.
Citizens of European nations, the US (not flying from the U.S.), Canada, Australia and New Zealand are able to purchase a Cuba Visitor Visa online from Cubavisas.com. This is one of the quickest and easiest ways to get your visa. You will need a return ticket before applying, and some airlines will not allow you to board a flight to Cuba without holding a Cuba Visitor Visa.
Air Canada and other Canadian airlines include the Cuba Visitor Visa as part of the air ticket and it is handed to passengers on the plane, but you should re-confirm this when buying your plane tickets.
Cuba tourist cards are also purchasable at many airports in Mexico, Central America and the Caribbean when you check in, with the process only taking a few minutes. If you plan to buy your visa in this way, please ensure the service is available at the airport you intend to fly from!
Another option is to contact your nearest Cuban embassy or consulate. They usually exist in capital cities and larger cities where there is demand, and you can find a list of diplomatic missions worldwide here.
It is important to note here that Cuba-US relations continue to change. Currently, those applying for a Cuban Tourist Card for travel from the US to Cuba get a special pink version. If you are traveling to Cuba from the US (whatever your nationality), you theoretically need to fall under one of the 12 approved travel categories. Independent people-to-people travel is no longer an available option, however those who consider themselves to belong to this category of traveler can choose the 'Support the Cuban People' category of travel when applying. Further detail is available here:
Making things easier, generally speaking, if you are flying from the US, your airline will sell you the pink version of the Cuba visitor visa during the check-in process for your flight (or direct you to another desk nearby where you can purchase the visa). Alternatively, Cuba Tourist Cards can be purchased in advance through websites specialising in US-Cuba travel such as: