I agree with wild spot in that I don't make a big deal about WHERE my mare is in relation to me. More importantly is that she has good leading manners - she stops when I do, without any pressure on the lead rope. If I take a sharp turn, she must go with me. If I back up, she backs up too. It takes some work, but you should be able to have complete slack in the leadrope with your horse moving with you, wherever you go.
^^ This-unless I know it is a really spooky crazy or green horse, who doesn't yet know the "rules". Then I pay more attention to my position and control them more with a slightly shorter lead. I still demand they stay their distance-with a simple twirl of the end of the lead. It only has to "accidentally" hit them in the nose once, and they understand. I also use the same twirl of the lead to move other horses in the pasture away when they crowd me or the horse I am leading.