If you wish to have an authentic Finnish sauna experience, you need to feel connected to the nature. The best way to do that in the city or in the middle of winter is to enjoy a natural birch sauna scent in your sauna. The scent of genuine birch leaves is what we Finns always connect to our traditional sauna experience. It relaxes and calms us and brings back happy childhood memories from the Finnish summer cottage life.
Otherwise, there aren’t many specific rules about how to sauna. Well, it would be good to avoid cursing and talking about politics. In sauna, it's good to listen to yourself. Stay as long as you like. Have as many cooling pauses as you need: outside, in the lake, on the balcony, in the shower. Breath in the scent of birch, dream of Finnish summer and enjoy!