The finger that today we know as the �ring finger� was not always the finger of choice for the Wedding band. During the 1400�s, in certain European provinces, Wedding rings were worn on the fourth finger of the right hand, and later on, fashion and trend led to ladies in the 16th and 17th century wearing them on their thumbs.
The idea of the vein/heart thing (vena amoris) may well be traditional belief or legend, but sadly (for the true romantics) a myth. But a nice one. Why we really ended up with the 3rd finger nobody really seems to know, but suggestions are that it was through religious ceremony in medieval times (placing the ring on the thumb, then first finger etc etc recounting 'in the name of the father, son, holy spirit, with an Amen on the 3rd finger). Others suggest it is the weakest finger on the least used hand, and therefore just most practical.
I don't know whether that is true about Germany, but wedding rings are worn on the right hand in Norway, Russia, Bulgaria, Poland, Austria, Denmark and Latvia amongst other countries.