Socializing and celebrating at the same time can be done at the Helsinki Cathedral where the bells are rung at midnight on New Year's Eve. This is followed by fireworks and New Year's celebrations outside, depending on how cold the weather in Finland is at the time.
Many New Year's parties in Helsinki are private parties, so if you know local Finns and can attend a private party, you're guaranteed a good time. As a visitor, you can visit local clubs and bars on New Year's Eve, most of which may be rather quiet but often still have special parties on December 31. All in all, the streets are fairly quite compared to other cities on New Year's Eve in Scandinavia.
At a privately held New Year's Eve party in Helsinki, watching the fireworks is often followed by tin melting. You melt your piece of tin on a spoon and then quickly let the tin drop into cold water, where it forms a shape said to foretell your future.
Helsinki's New Year's Eve parties often offer buffet-style meals along with locally popular drinks and sparkling wine.
And how do you say Happy New Year in Finnish? "Hyvää Uuttavuotta".