My favorite thing to do with them is to practice when we have all the time in the world, no vet appts, no trail rides, nothing to do but on and off. With those little 2 horse straight load trailers, I like to walk up to the back, let them sniff and walk away. Several times until they aren't at all hesitant. Then I like to see if they will follow me in, even just a step or 2. If they will just put a foot or 2 in, I stop, let them rest there, pet them and tell them they're good and back out and walk away. I like to break things down step by step and not do more than about 20 mins at a time. Then take a 10 min break and go back and pick up again. It takes a while but it works.