Helpful Hints
If you want to go to Cuba... Go! You'll love it, but i thought i'd write down a few things you might find useful. Bear in mind that i'm a student, and having next to no money, this is how we survived:
Accommodation
You don't need to book anything, although we did via email for the first couple of nights. Many Cubans make their money from letting out rooms to tourists, and they'll treat you like royalty - often you'll get breakfast as part of the price and dinner as an optional extra. They will also guide you to their friends and connections in other parts of the country, so it's easy to find a place to stay wherever you are. In fact getting off the bus in a new town, you'll be hounded by people offering you a place to stay - this is a great way to meet genuine Cubans, its safe and inexpensive.
Safety
Guide books will give you more details, but we didn't have any trouble. We met one guy who had his bag snatched in havana, but there are police on EVERY corner in havana, and if that doesn't make you feel safe, nothing will. Obviously take the usual precautions, be aware and look out for eachother.
Money
Cubans use pesos, but tourists will have to use dollars mainly, meaning you pay 20x what locals pay for the same good. Keep an eye out, some small stalls and shops will accept any pesos you can get your hands on, which means you can get a cheap ice cream or pizza. There are plenty of places where you can exchange dollars/travellers cheques, but remember, no american credit cards etc will be accepted.
Language
It does help if you can speak spanish, as we found out speaking little between us. However we made the effort to know the basics, so that we never seemed inpolite. Having said that, it's a difficult version of spanish to understand, and a lot of people will be more interested in practising their english on you. One guy we met, a security guard, wouldn't let us leave him until he had learnt a new english phrase.
The Hustlers
You WILL meet these, and get to know some individually if you stay in the same place, particularly havana, for a while. You'll be constantly bombarded with offers of cigars, women, private restaurants, drugs etc. Its up to you what you choose, but if you don't want anything try not to get annoyed (even though it is annoying) because they are only after a living. We found it best to smile and say no firmly.