Do I have to make a reservation in hotel before I go to Goa?

I have a plan to visit Goa, India end of November 2008. I want to know if I have to confirm my hotel reservation before I go there. Will it be risky to search for a hotel after I go to Goa? ... rooms were completely different and dirty from what we were told.. and there were rats in the room as well.. sometimes its a better idea to go to the place and book.. atleast that is what we decided.. and with sooo many hotels in goa u will get a room in some nice place for sure ...