Some good advice for travel to any destination:  Pack all valuables in your carry-on luggage.  Theft from checked baggage can and does happen at airports around the world.  Whenever and wherever you travel, the valuables you have with you are the safest ones.  This is sound advice that will prevent loss of valuables in case of lost luggage, as well.

Cubana, the national carrier of Cuba, is great.  They make all announcements in three languages and the drinks are inexpensive.  The new airbus 320s definitely have more legroom than any other charter and the seats are less cramped. Interjet, also with more than average legroom and often offering online discounts, flies direct from Cancun (CUN) and Mexico City (MEX) to Havana.

Otherwise, Copa (via Panama), Taca (via San Jose, Costa Rica) all fly there, as do KLM (Amsterdam), Virgin Atlantic, Air France, Air Transat (Canada), Iberia and Condor (Germany).

 It's a less expensive option for travelers from London who want to vacation in Cuba. 

You can fly Blue Panorama airlines from Italy - a flight Rome to Havana return will cost about 700EUR (tax incl.)

Once you arrive at La habana, for example, the passport queue is very long and then you have to go through security. You may be asked (in Spanish) if you have been to Africa in the previous 30 days. Then there is baggage reclaim. All this takes at least an hour.

There are two money exchange offices just outside the airport by the taxi rank, and one in departures, which is probably quicker.

A taxi ride from the airport to Havana centro takes roughly 30 minutes and taxi is really your only option. There are no public buses to or from the airport. The taxi should cost 25 CUC into town but you might get a much cheaper deal if you take a Lada taxi rather than an airport one - they could cost as little as 16 CUC. You could even try your luck on the departures floor and flag down taxis which are dropping off passengers - they should charge less; it's the airport taxis which really rip you off. 

Another option on the way back to the airport is to grab a taxi that is NOT parked outside a hotel or simply negotiate a rate.

If you are flying back to Europe with AirFrance, don't buy duty free at Havana Airport, they confiscate it at Charles de Gaulle, saying it is not allowed because it does not come from inside the EU. If you complain, they suggest you go to an office, which would mean missing your flight onwards.Perhaps that those security staff never have to buy any booze.

Since May 1, 2015, the departure tax is collected by the airline, when tickets are purchased.  The departure tax booths at the Cuban airports have been closed since that date, and it is no longer necessary to pay departure tax when leaving Cuba.

You can exchange any CUC back into Euros, Canadian Dollars etc, inside the departure lounge, but they sometimes run out of small bills (€5, €10 etc).