When it comes to getting our horses into trailers, we instinctively do everything wrong. So, to succeed, we have to learn to do things better, smarter, and to overcome our innate predatory drive to make the horse get into the trailer.
Here are some rules:
First, as a general principle short of a true, life-threatening (i.e, your horse is seriously sick or injured and where you may to just resort to a block and tackle), we can never, ever force a horse into a trailer. As I have written about trailering extensively in my book, Zen Mind, Zen Horse [pages 125-131, 279-284], the key to getting our horse to calmly, reliably, easily, and willingly trailer are these:
1. First train your horse to trailer when he’s tired, not when he’s fresh at the beginning of the day. He will be less reactive when he is fatigued and more inclined to find the least energetic solution, i.e., loading onto the trailer.
2. Always practice making your horse backing up straight.
3. While training your horse to trailer, never disturb him when he is standing quietly on the ramp or in the trailer space. This includes sniffing, nosing, tonguing, biting, and pawing at the trailer. This is a sacred moment. The key to building the horse’s confidence is for him to believe the trailer and ramp are safe places. If you start pressuring your horse when he’s investigating or checking out the trailer he’s simply going to say to himself: “Yep, I was right. There’s no peace to be found in that trailer. As soon as I try to figure out what it’s about, somebody starts tapping on me with the end of a rope or a whip.”
4. Do not close the ramp or the trailer doors even for a split nano-second until your horse has climbed in and out of the trailer at least one hundred times.
5. Keep your trailer parked close to the barn so your horse(s) can practice loading every day.
6. The more your horse wants out of the trailer, the more you want to make him work outside the trailer. In other words, standing on the trailer is a break, getting off the trailer is getting back to work, moving his feet, running around, getting winded, and so on. The harder your horse has to work outside the trailer, the better the inside of the trailer begins to look. After working a while outside, the horse looks inside and says to himself: “Hey, my owner really fixed this trailer up nicely from the last time I looked in here.”
7. Always invite your horse into the trailer (that means don’t pull on his lead rope!) but it is always your horse’s choice as to whether to accept the invitation or not. If he declines the invite, then it’s time for him to do some physically demanding work outside the trailer. The alternative to running around is to stand quietly in the trailer. Eventually your horse will catch on and dive for the inside of that trailer!
8. Never let your horse turn around inside the trailer and head for the exit nose first! Horse must always step in straight and back out straight.
9. Get a ramp. I know. It’s like being Republican or Democrat. You either vote for a step-up or vote for a trailer with a ramp. I am solidly in the ramp camp. Ramps make it much easier for your horse to load and unload patiently and slowly. Ramps just make a horse feel safer and more confident about where they’re putting their feet. The more confident the horse, the easier he’ll trailer.
10. The more you practice trailering, the less you’ll ever find yourself with a horse that gives you trailering problems. The less you practice, the faster your horse can turn a chance to trailer into a day in hell.
11. Trailering is about patience. It’s the essence of giving up our predator nature, of forgetting about how the horse gets into the trailer and focusing on how our horse feels about the trailer.
Happy trails…and trailering.
 Before I get a thousand letters and emails, no, I’m not recommending you use a block and tackle. I’m trying to make a point. That said, if my horse was dying and the only way I could get him into a trailer to get him to the animal hospital was a block and tackle, you betcha I’d use it if nothing else would work.
 As a rule, never practice loading horses onto a trailer that is not hitched to a truck. Loading a horse into an unhitched trailer can actually lead the trailer to lurch unexpectedly in the air. A no-no.
 Don’t get your horse so winded, he cannot catch his breath. He will just stop thinking when he gets too short of breath. To the contrary, you want to keep offering your horse breaks near or inside the trailer where he’s got plenty of time to catch his breath.