With work etc I don't get all the time I'd like to work with my horse. So for me leading is incredibly important and I always use it as a chance to reinforce the relationship.
We have a simple rule when we go for walks or even leading down to the pasture. If I stop and pull a handful of grass he can eat. If I don't he does not pull down to the grass.
A lot of people will suggest working the horse - so if he goes down to grass make him move his hindquarters etc, but unless the rules have been set ( for example as above) then although this can work, it does often build resentment in the horse or a loss of spirit again as I so often see these days.
Personally it's a wonderful opportunity to develop your presence. For example when he goes down to eat interrupt him the moment he thinks of it. Interrupt him with a flick of the line, moving your body sharply back towards his rear, or simply suddenly move into a trot and ask him to follow.
Either way it 1) interrupts his eating without pulling or physical contact. And 2) further strengthens your control.
Incidentally there is a fantastic example here in this old video from KFH - if you can hold a stallion back from a mare in heat then grass shouldn't be a problem! Lol http://m.youtube.com/index?desktop_u...?v=lQULL3jA3TQ
(I couldn't get the URL thing to work, so either cut and paste or just put Hemplfing Leading into You Tube search)