Money is best in American currency and exchange to Rubles in small amounts ($100 US at a time). Remember it is illegal to take Rubles out of the country and you can't purchase Rubles outside the country either. You can get a higher rate of exchange if you use the Black Market, but it is best to use the Money Exchange outlets (they are everywhere). No Russian language required, just shove your passport and American Money or Euro's in tray door and they will exchange it, they may ask you if you want a document noting the exchange, but it is not necessary for you to have, but it is for them. Russia has just changed it's money again, having dropped 3 zeroes in the denomination ( 50,000 Ruble note now = 50 Rubles). Russian coins are also now being used again.

As for credit cards, many places are now starting to accept credit cards, but be warned many establishments also display on the door they accept credit cards but upon time to pay won't accept them. You will also have a difficult time getting businesses to accept travelers checks, best to always pay in cash. It is best to bring with you US $ or Euro's $ only, other currencies can be difficult to get exchanged.