Jigging and shying on the trail is a big problem I've experienced a lot, and refusing to go over obstacles (ditches, puddles, logs, etc.) are some of the problems I have had the most trouble with. One of the more serious problems I have had on the trail is my horse spooking and trying to run back to the barn, I fell and broke my arm on that one... mostly that was a problem with my horse's fundamental training, I should not have had him on trails yet. But that is a common problem: Barn sourness.
Those are just a few suggestions. Let me know how it goes. I would love to hear what you have to say on the mater.