If you stay at one of the swank hotels, do NOT get your dollars changed at the hotel counter - you'll end up losing money. Especially if you (like I did) have to change from $ to RR and then back again!
Unique Suggestions: If you can't make it out on the street, make it a point to pay by credit card. You get ripped off for slightly less because the bank rates USUALLY apply.
Fun Alternatives: You can get a much better exchange rate at any of the shops out on the street. I saw quite a few on Kutuzovsky Prospekt.
Credit cards are not widely accepted. I like to pay with a credit card and do it each time I can; and I still about 50% of my monthly budget is spent in cash.
You may pay with credit cards in large supermarkets, good (read expensive) restaurants, boutiques and that is all.
A passport or driver's license are often needed as a confirmation. Same time, the sales stuff don't even look at your signature often!
Unique Suggestions: Hopefully, there are 24 hour ATMs in the center. Just ask your taxi driver to drive slowly and you'll notice them.
Fun Alternatives: The following is considered as a crime, but you may try to pay in US dollars and it works often in small clothes shops, on the markets, in beauty shops, flower shops etc. It's treated as normal, and I never heard anybody was arrested for this.
Still, this is at your own risk. I do it only when I feel I can and if there're no money exchange around.
Never exchange money in the hotels. The rate is always worse than on the streets. You shouldn't either exchange on the black market, but in exchange offices offering their job almost anywhere in the city.
On my short business trip to Moscow, the officials warned me about the tricks that the people in the exchange booths in the street use to rip you off. They count the money and when handing it to you, some glue will make sure some of the money sticks to their hands. You won't see it and as you counted together with the staff, will not double-check.
Unique Suggestions: Do not exchange money in the booths, but change it in the airport or hotel or withdraw it in a ATM. Not all hotels exchange money!
You will pay high prices from everything to coffee to meals. If you are hungry in red square buy an ice cream from a local vendor and eat elsewhere.
Unique Suggestions: Sit in the park area and enjoy the people. Also, they sometimes have shows in the warmer weather.
Fun Alternatives: Try other areas of Moscow