How do I buy a diamond ring?

In Sweden, Denmark, Finland and Germany, both the man and the woman wear engagement rings. However, in these countries the man's engagement ring is often used as the Wedding ring. (In Germany often the engagement rings for both partners are plain gold or platinum bands, worn on the left hand, which are then moved to the right hand and used as the wedding bands once they get married.) The female usually gets a diamond wedding ring. Nowadays some men wear two rings, but this is still rare.