Walk around old havana and the old square
Have a drink in La Bodeguita del Medio (where hemmingway used to drink, be careful prices are high!)
Go to Tropicana to watch a show (not cheap but very good, book early when you arrive)
Visit a cigar factory (tourist favouite but worth a quick visit)
Stand at the Plaza de la Revolucion
Hear the canon at La Cabana Fortress each evening
Walk to a section of the old city walls
Take a drink in the Park Nacional hotel
Eat at a Paladeras (Local family restuarant) down a street in Habana Vieja (agree how much before you order!)
Take a coco taxi