Left hand 3rd finger is American way. When wearing both wedding band and engagement ring on same finger, the wedding band is placed closer to the palm, i.e., closer to the heart. Russians wear wedding band on right hand 3rd finger.
@Nechoma – emthe second finger of her right hand (the finger where the chassan puts it on her during the chuppah)em
The finger the chosson puts the wedding band is the index finger (pointer) on the right hand in all the cases I know about. Then the kallah transfers it to her 3rd finger left hand at some point.