1. A smile in Russian communication is not a sign of politeness. Western smiles when greeting someone mean pure politeness. The more a person smiles the more friendliness he / she wants to demonstrate to your partner. Constant polite smile is called in Russian 'duty smile' and is considered a sign of poor human manifestation of his insincerity, secrecy, unwillingness to find true feelings. Russian smile - is a sign of personal sympathy, and not polite.
2. The Russian did not smile at strangers. Smile in Russian communication is addressed mainly familiar. It is therefore not a saleswoman smiling customers - they do not know them. If the buyer knows the saleswoman, she told him necessarily smiles!
3. Russian atypically smiling back. If Russian sees smiling to him / her a stranger, he would certainly be fun to find the cause. Maybe something in his / her clothing or hairstyle made this type so much fun.
4. To Russian smiled, it should be for this reason enough obvious to others. It gives a person the right to smile - from the point of view of others. In Russian, there is a unique saying that is not in other languages: "Laughter for no reason - sign fool».
5. Russian unsmiling man (that's unsmiling, not gloom - Russian mostly funny, cheerful and witty) and supported by Russian folklore, where we find a lot of proverbs "against" the laughter and jokes. Dictionary of Proverbs Vladimir Dal Russian people - Joke to no good arguments. - And laughter leads to sin. - Humpday. - Sometimes laughter crying responds. - In truth there are no jokes. - Joke lead to no good.
6. Do not accepted Russian smile on duty, in the performance of any serious business. For example, customs officers at airports never smile as busy serious business. This feature is unique Russian smile.
7. Russian smile is designed to only be sincere, it is regarded as a sincere expression of good mood or location to the other party.
So, if you smile a foreigner - it does not mean anything, he was taught to smile at everyone, and if Russian smiled - he did it because they really wanted it.