According to the regulations of the Customs Union, of which Russia is a member together with Belarus and Kazakhstan, certain items should be declared even if they are imported or exported for personal use.
See the Federal Customs Service official website for detailed information. The language of the website may be somewhat awkward, but it is official and, hopefully, updated.
Avoid advice and assistance of companies, individuals and unofficial sources which may be outdated and (or) otherwise misleading.
Pay particular attention to the regulations governing exports and imports of weapons, antique items, artworks and other expensive goods, including caviar. Save receipts for such items.