Helsinki city
City side
It is rare for a Finn to open the door of his home to you. If you do, it is a great honour.
It is imperative that you are on time. A quarter of an hour late would be an insult to your hosts.
It is always the lady of the house who is given the small gift. Stick to the classics: flowers (it is customary to unwrap the package before entering, to give flowers without paper), chocolates, wine (French is even better).
It is customary for ladies to bring a spare pair of shoes. Indeed, everyone takes off their shoes and the shoes are usually stored at the entrance. Men, on the other hand, often stay in their socks! Your hosts will probably not dare to ask you to do this, so think about it for yourself, it will be much appreciated.
At the entrance to most public places, cloakrooms are available for a fee and are sometimes compulsory. If you have a dress jacket, you can keep it on, but no nightclub doorman lets you in with a jacket. On the other hand, no problem with a heavy jumper thrown carelessly over your shoulders. You don't try to understand and you just do it; in Finland, you NEVER argue with the rules or the instructions.
It's not a good idea to interrupt someone's conversation. It is even customary to wait 1 or 2 seconds before answering, as it is possible that the person you are speaking to has not finished his or her sentence.
Field side
In Finland, you can walk, ski and even camp on any land (except nature reserves, beaches and public areas), as long as you do not trample cultivated fields and do not disturb the owner's privacy, which implies that you stay at a reasonable distance from the houses. This is especially true for holiday cottages, especially on the lake side (which is often accessed by a path): in this area, a Finn will not tolerate seeing or hearing his neighbours, who must keep a minimum distance of 100 m and avoid any noise that is even slightly loud. Be sure to observe the signs indicating private property, "Yksityisalue" (in Finnish) or "Privatområde" (in Swedish).
When staying overnight in a hut and using wood for heating, always remember to replace it. An axe is available for this purpose. Not doing so is rude. Don't leave any rubbish: always take away all your non-compostable or burnable rubbish.
Picking berries and mushrooms is allowed. But where there is a right, there is a duty: to respect nature, which is made fragile by the short duration of the summer. There is no question of causing the slightest damage to plants or animals, of driving off-road or of throwing the smallest piece of waste on the ground or in the water. You may not light a fire or collect wood without the owner's permission. Dogs must be kept on a leash from 1 March to 1 August, to allow wild animals to breed in peace.
Finally, it is strictly forbidden to enter the protected natural areas, marked with the signs "Luonnon suojelualue" (in Finnish) or "Natur skyddsområde" (in Swedish).