after many years i have a BIG network of swiss folks, but there are only two who i visit without a 3 months notice TERMIN. if you are somehow spontaneous you'll have to get used to schedule your social life exactly the same (or even more formal) as your business life. forget about to show up with a pack of beers to watch the football match just because you "feel it".
being in sports are a good way to make friends. not girlfriends though