It depends on the horse. If he's young and spooky, pony him a few times and then take him out with another horse a few times. If he's a sensible horse generally, introducing him to trails shouldn't be a big deal, just hop on and head out. If he needs a friend to help settle his nerves, by all means make it easier for him rather than harder till he gets familiar with the new sights and sounds and footing. There's nothing better for trail prep than actually being on the trail, it's not necessarily much different than pasture life, depending where your horse lives.
don't worry, spiders, I keep house casually.
~ Kobayashi Issa
(1763 - 1827)