Is it necessary to book accommodation in advance ?

Our advice is: book the first few nights in Havana, then book as you go. Do it in private houses: they are the cheapest way to stay and allow you to have real contact with the Cubans.
On the other hand, if you prefer not to waste time and energy in finding your ideal house, you can make reservations before arriving in Cuba. We advise you to have a look at this web where there are many options, always in private houses