The Metro and Subway in Moscow and Saint Petersburg is amazing. It takes you just about anywhere you could want to go, and quickly. It is in need of some air-conditioning, as it gets quite warm down there in the summer. It’s cheap to use, but they no longer use the Metro tokens. They have now gone to a card system. The price varies depending on which one you purchase. They are the same size as a credit card and pushed into a feeder that stamps them upon recording each use. Be sure to look at the amazing architecture, marble stone works, and statues throughout the Metro. Most of the Ring Stations are the ones of real beauty, with a heavy influence of Soviet Propaganda of course. But there is no English in the Metro so use a Russian metro guide unless you can understand how to translate English to Russian for the different Metro stops. Try to get a Metro Map that has both Russian and English. The Moscow Metro can be very overwhelming as it is so large, but after you use it a few times and understand what stop or station you want to get to, it becomes fairly easy to use. In Saint Petersburg the Metro is much smaller and easier to use, but still is very useful. Do push on when boarding a subway train, Just do not get angry, imagine you are pushing thorough the bushes in the woods. Also it is still customary to give up your seat for elderly and women with children. Children under 5 are free.
Money is best in American currency and exchanges 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 these, but be warned many establishments also display on the door they accept credit cards but sometimes won't take 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.