The taste of strawberry kompot brings the taste of my holidays I have spent at my grandma's place far away from Warsaw as a really small runt :)
I might not be Russian, but as being a slav Лѧхъ desendant, having met some Russian, Belorussian and Ukrainian folks and having some experience exploring Moscow and Crimea some years ago I would like to indulge Berg with some personal recommendations:
1) You should try kompot with cold noodles (eaten like a soup) if you get a chance - it is great for hot afternoons.
2) Watch the traffic in Moscow man. It is a sight to see if you are used to German traffic :)
3) Learn "blin" and "blyat" terms. You will hear that a lot in different context. Using them properly by yourself will yield you a lot of hugs and drinking invitations.
4) Be sensible. It took me some time and stress to grasp the amount of Soviet Union sentiments of older folk there. Poland has been in the Soviet area of influence after WWII what almost led to a civil war and made us invest more than 50 years into a failed political project called communism (yep, I am very biased here since some of my family was killed in that turmoil). I was really put off with this and confused at this fact, but then started exploring this bias. And the point that everything revolves around here is that Americans have their good old days defined as the '60s or '70s while Russian good old days are the communist era. If you understand that and show respect due the fact that Soviets sustained the heaviest losses in WWII - you have a common ground for mutual understanding.
Holding onto something bigger to find your comfort and your inner strenght when facing not so ideal reality on everyday basis is the survival tactic of humankind since tribal times - this is what personal experience of drinking both with easterners and westerners has taught me. Due respect and a some genuine interest in Russian way of life will open their hearts broader than Mussorsky's great gates of Kiev.
5) Embrace the experience - Russians on the general are a bunch of wonderful people with great history and will treat you as an honoured guest unless you behave like an intruder.
6) If you can still buy vodka in plastic 200 ml yoghurt containers with tinfoil caps - buy a bunch of them and take home. You get a very fun and rare gift fitting for every possible event on the go!
7) Plenty of places to see there. Kremlin and the Red Square are a must.
8) And this one is crucial! Always stay cheeki breeki :)