A name and an address, write the letter, and put it in the addressed envelope. Go to the post office and tell them you want to send a letter to Switzerland. They'll handle the rest. Oh yeah, international postage is expensive.
If all you have is a name and a hometown, you need some luck. Hopefully the guy is a) still alive and b) still living there. If the town is small enough, it should go through with just the name and the town for an address. This works more often than you'd think since Switzerland is such as small place. Otherwise, you need to find a more specific address. I have no clue on how to do that one.
Another problem is that a lot of older Swiss don't read English. He'll find one of his younger relatives to translate out of curiousity if he doesn't, most likely. French or German might make it easier on him if you know either.