If you change a dance video to a mirrored one to learn it.

If the video has been mirrored, then your movements should be in the same direction as what the person in the video is doing (from your point of view), e.g. if he's doing a left hand (his point of view), then you're doing a right hand (your point of view), i.e. like looking in a mirror, so that the whole dance doesn't go the other way around.