I haven't gotten the Rohan expansion yet, and I'm not high enough level to get a war-steed. So I don't have in-game experience yet. But I have read a lot about mounted combat on the Lotro wiki and I've watched some videos about it and it seems very similar to mounted combat in the Medieval RPG strategy game, Mount&Blade.
I will post links to guides and videos here about mounted combat in Lotro. I might make my own guide later on, but right now it will only have links. Anyone is welcome to post info or links to guides and videos about mounted combat so I can add them to the thread.