just got back and thought i would just put some things on i found usefull during my trip so people researching theres can consider doing the same. i stayed for 3 nights in havana at the nacional.
1. do a tour with jorge thats mentioned on here. if its your first time in havana this will save you time in finding the things you want to see, give you a chance to pick up some usefull info on the city and in general its just a great tour.
the service is top notch and the tour guides superb. we done the driving tour the next day as well and for the price it was more than worth it.
i think this tour gave us a great grounding for getting around the city.
2. take a guide book. we used the rough guide to cuba and its maps, reviews etc etc were all accurate and again probably saved us a lot of time, effort and poor meals.
3. try and know a little spanish. this will really help in havana. i also get the impression that speaking in spanish makes you a little less likely to be ripped off as you can come across as knowing what you are doing even when you dont.
4. expect to be harrassed. you will be asked the same few friendly questions over and over and over before your finally asked to go to a certain bar, buy someone a drink etc etc. just be polite and firm and you will be fine. outside of that though we never had one instance of being ripped off at a money exchange, inflated bills or even being given silly prices by taxi drivers which i have had pretty much everywhere else i have been in the world.
these may be four basic common sense tips but they will help you get the most out of your trip.
one last one would be to visit the paladar vista mar in miramar...try and get a balcony seat the views are amazing.