The tradition of a wedding ring is an ancient one, and has spread far and wide from its origins in Europe. It is typically the best man who carries the rings and gives them to the officiant or the groom during the ceremony. Needless to say, the best man is responsible for the rings and he should be able to provide them promptly when requested.
A ring is generally circular in shape and it has the meaning of unity, wholeness and completion in many cultures. Sometimes people exchange rings and other times it is only the bride who receives the ring. Traditions vary but i would encourage people to do it in fashion that suits their personalities. The more you weave your personalities into the actual wedding day, the more special it is for you and your guests.