Baltic States + Russia: There is a close relation between food and hospitality in Russia. From the moment you visit a Russian home there will be food on the table. You are constantly encouraged to eat more by the host. Keep in mind that refusing drinks or food is seen as an insult in the Russian culture. Another form of hospitality in Russia is sharing things like cigarettes, food and drinks. This is even a cultural rule when you share a compartment with strangers in the train for example.
Bring a small present like wine, pastry or flowers when you are invited by a Russian. Make sure the number of flowers is odd because an even number of flowers are associated with funerals.
In Russia people expect men to behave politely; this includes holding the door open, standing up for women in public transport, et cetera.