The local currency is the Kyat (pronounced "Chat"). However, It is recommended that you take US dollars - small notes. They should be pristine, no folds, no marks or turned over corners. Also do not take dollars with the serial number beginning with CB as they will not be accepted. Even tips cannot be given with marked dollars.
Credit Cards are rarely accepted. If you do find a hotel that will take them they will charge you a hefty % charge. You can change dollars into Kyat reasonably easily at the airport. You cannot obtain the currency before you arrive in Burma. (US$1 is approximately 960 kyats but this alters daily).
You will find cashpoint machines in some larger towns and there is now one in Nyaung Shwe. But many of them charge up to 10% service charge on any cash withdrawal.