Here are some quick tips about Havana.
in Hanoi bar (a.k.a. Hanoi bucaneros) near Hanoi restaurant, calle brazil between bernaza and monserrate, 1 CUC, very good, serves some food, too.
In Bodeguita del medio you can go only for historical reasons. A forgettable mojito in the bar costs 4 CUC.
Best pizza: in calle o' Reilly between aguacate and compostela, 10 to 15 pesos, only take away.
Best fried chicken and beer: in the bar on the sea front in avenida de cespedes, near plaza de la catedral. Fried chicken costs less than 2 CUC, beer the usuals 1.15.
Ice creams (in pesos) in obispo 58, are quite good and usually there are not queues.
The Coppelia shop in CUC is outrageously expensive.
Turistic double decker open top bus is worth the price, even if used for transportation: with a daily ticket (5 CUC) you can reach various destinations (vedado, plaza de la revolution, playas del este, la cabana, marina Hemingway) inside and outside the city.
If you can, don't give money to beggars: it's even less fair than in the rest of the world.