The wedding ring is the most important object in a wedding ceremony other than the two people involved who obviously cannot be referred to as such. The rules surrounding which ring goes on a given finger differs by culture and sometimes by country. This can make a wedding ceremony that tries to incorporate more than one tradition complicates. In order to dispel confusion and to explain some of the rules, here is a short overview of wedding ring etiquette.
In the west, where Roman Catholicism and Protestantism are the most common religious traditions, the ring is worn on the left hand. This includes countries such as France, Ireland, the UK, Mexico, Italy and the US, to name a few. The reason for the use of the left hand is because it was assumed by ancient civilizations that there was a vein that ran from the third finger of the left hand directly to the heart and by wearing the ring there you were showing your affection in the most overt manner possible. However, in the Eastern Orthodox Church and other countries, even some in the west, the ring is worn on the right hand, such as in India, Russia, Poland, Greece and Germany.
Some interesting deviations from the most common traditions are the Indian tradition of using a toe ring called a bichiya and the bangle used in West Bengal in lieu of a wedding ring. Other cultures, such as the Japanese, traditionally did not have a diamond ring involved in any ceremony, although this has become quite popular over the last 50-60 years.
In terms of the proper etiquette at a wedding ceremony, the best man traditionally keeps the wedding rings, although he may hand them to a ring bearer in a fancier ceremony, who carries them on a large pillow or cushion. During the wedding ceremony and afterwards, the engagement ring is worn on the right hand and the wedding ring remains on the left hand. Some people may combine their engagement ring settings with their wedding rings, although this is usually at a later point in time.

