Keep in mind that tickets to
popular museums such as the
Armoury Chamber,
Diamond Fund, Cosmonautics Museum, Pushkin State Museum or Tretyakov Gallery are usually hard to get, especially during high season (from May till September). So, take care of this in advance, visiting museum's websites or
booking a tour with skip-the-line tickets included.
Getting a local SIM card will make your stay in Moscow much more comfortable. It's possible to find Wi-Fi almost in every café or restaurant, but often you will need a local phone number to connect. Besides, with unlimited internet you will be able to use google maps, TripAdvisor or other apps anytime while you are exploring the city. The cost is about 5 dollars, so, totally worth it.
If you get lost or need something, do not hesitate to ask the locals for help. Choose youngsters, unlike Russian babushkas (old ladies) they usually can speak English or other foreign languages. You should know that Russians in general do not smile to strangers, however this doesn't make them unfriendly or unhelpful. During the Soviet times because of the Iron Curtain, tourism was almost non-existent, so nowadays Russians have a very positive attitude to foreign guests.