When you land at La Habana you have two ways to get out of the airport and arrive at your destination in the city.
-The easy one is taking a taxi: if you take the ones waiting in the line just in front of the Terminal you'll probably pay 25 $, with small possibilities for negotiation...if you want to pay a bit less you can try to walk a bit farther and ask to the ones that are parked outside the line; I was offered a ride to the Habana Vieja for 10 $ but I refused because a wanted to try the second option, as you will see....
-The funny and cheap one is taking the bus, it will cost you only 10 cents $ but I have to admit it was a really punk experience.
If you are coming from abroad your plane will land at Termanal 3, the first thing you need to do is going to Terminal 2, the one for local flights, to get the bus for the city.