I want to write a fairly detailed letter to some friends in Finland, but I'm unsure on the etiquette, for example:
- How to say, 'Dear..' and 'To..'
- The equivalent of 'yours sincerely, faithfully' and 'with respects'
- positioning of your address, theirs, date etc on the letter
Also I can't figure out how to say 'How are you both', I can can say 'how are you' and 'both' separately but I can't put them together properly..
Well, I'll give it a shot, but it made me laugh a bit because the idea of Finns being so polite in a letter is quite absurd
Just how formal do you want to be? If they're your friends, you can simply write 'Hei'. Hei goes for anyone from your friend to... for example, an otherwise unknown person at university (eg a student advisor), when writing to KELA to ask about stuff... I've only seen things like "Hyvä X" and "Arvoisa X" in extremely formal letters such as to members of consulates and in some letters from a company to its customers (in which case the most common is Hyvä asiakkaamme - Dear customer).
You can also use 'to' by adding the suffix -lle to most names. I'm not sure what their names are so I can't tell you how to form them with regards to consonant gradation.
Summary: I'd use hei. Or the -lle case.
Yours sincerely/yours faithfully is best expressed with '(Ystävällisin) terveisin'. It means "with (friendly) greetings". For some reason I find 'terveisiä' a bit more friendly, since 'ystävällisin terveisin' is usually what you get from people you don't know too well who have to be polite to you (sometimes to the extreme of Yst. terv.
Summary: terveisiä to close friends, ystävällisin terveisin to others. In very informal messages you can also write t. Your name. (t = terveisin).
The latter I'm not sure about. Finns have mostly used e-mail with me. I just dug out a bank statement
and it has
BANK NAME ...................................................... STUFF ABOUT ME AND MY ACCOUNT
But I'm not sure if it's like that just because my account details are at the top.. just looked at a letter from the post office and it did the same