I don't know about you but the first things I want to learn about new languages are numbers, greetings and swearwords. I think this gives me a good base from which to continue. I'm particularly interested in the different ways people swear; in Romance language countries there's more religion-related swearing, whereas in the North of Europe there's more emphasis on excrement and genitalia. Poo :D
I know from experience that it's a bit embarassing to ask a teacher for swearing vocabulary so here you go:
1) Oh shit!
This is a brilliant word, because as you'll soon see, it can be used in a variety of insults. It's not even particularly strong, so you can use it fairly often. Don't go crazy with it though, your insults pack more wallop if you save them.
2) Damn! Fuck!
Helvetti is usually translated as hell. Saatana is Satan, as you can probably guess. Perkele has only recently ("recently") been associated with Satan, before that it was associated with an ancient Finnish god of thunder, Ukko. Perkele is a particularly Finnish word, partly because of the aforementioned traditions, but mostly because Finns like to roll their r's. They think it makes them sound scary, a bit like how cats fluff up to deter perceived threats. It sounds better rolled, anyway.
3) Smell mould!
Finnish people are obviously further evolved in the olfactory department. A common method of insulting someone is to tell them to smell something which is unpleasant. Above is the example mould, but underneath I've written other examples. You can also tell people to smell shit or a vagina. Or anything you can think of. There are no rules. Go wild.
4) Egghead - beware
Egghead does not mean the same thing in Finnish as it does in English. Do not call your brainy friends eggheads. Egg in Finnish is a euphemism for male genitals. Calling someone an egghead is the same as calling someone a dickhead in English. I don't understand where they got the word egg from entirely, but I suppose a testicle could resemble an egg. Don't know why it's in the singular though. Again, you can use the word paska to form the insult "shithead" and the word kusi to make someone a "pisshead", which doesn't mean the same as drunk. No, a Finnish kusipää is an arsehole, and a Finnish pisshead is a juoppo (drunk).
5) Genitalia-related seasons
One of the most descriptive swearphrase in Finnish you can say is
Oh, spring of vaginas and winter-that-came-in-spring of penises! Takatalvi is like a cold spell that happens only when you've sorted out your clothes and put your warm winter thermals away for the year.
I don't really know what else to write about that one. I think it's best just to leave it in all its glory as it is.
There are more Finnish swearwords and insults, but perhaps I'll save them for lesson two :)