First you need to change your own mind set your horse will get on a trailer why because you are much more stubborn. Two you need a calm horse savvy helper. If they are not calm and patient and willing to do it your way then you have the wrong person. Three the person needs to be holding the lead and there job is to keep the horse looking straight. Every time the horse looks left or right they pull the horses head straight they are NOT to pull the horse forward at all!!! There should be NO forward pull what so ever. Why because your horse is going to walk on himself not be pulled on period. You need a lunge or dressage whip the horse should not fear the whip feel him or her over with it before you approach the trailer to make sure they are not bolting afraid. Walk up to a point where the horse stops then have the lead person 5-6 ft in front of the horse remember there job is to keep the horses head facing toward the back of the trailer only. Using the whip on the horses rear end tap ever so lightly and make a kissing forward noise little taps increasing in strength little harder….little harder….little harder keep going until the horse takes one step forward. The MOMENT the ONE step forward is taken stop with whip and kissing noise and praise and pet good girl wait at least 30 seconds then again. Using the whip on the horses rear end tap ever so lightly and make a kissing forward noise little taps increasing in strength little harder….little harder….little harder keep going until the horse takes one step forward. The MOMENT the ONE step forward is taken stop with whip and kissing noise and praise and pet good girl wait at least 30 seconds then again. Keep doing this over and over till horse is right at the back of the trailer or at the ramp. If the horse starts running back then instead of waiting the 30 seconds go right into the asking for the step forward. She only gets the 30 second reward if she is still. A couple of very important things. If the horse wants to smell the ramp or trailer allow it and praise. MOST IMPORTANT thing the lead holding person is responsible for if the horse places a foot on the trailer or two count to 5 OR if you feel the horse is about to step back, lead holding person backs her out off the trailer 3 steps. Every time the horse gets on and starts to back push them back off halt then start again with whip and kissing. Never ask for more than one step forward but if you get more then great! By backing the horse off the trailer yourself before they decide to back you are doing multiple things. You are establishing control of the situation as any good leader does and the horse is now thinking ok she is not only intent on getting me on she is intent on control of everything on and off. Gets the horses brain away from thinking all she want to do is force me onto this trailer. If you have a open stock trailer or if you can convert the trailer to be as open as possible. When you get to the point of ¾ on turn the horse around and walk off immediately. It’s your job to say I want you to get on but it’s not scary you can get off. This could take HOURS but after the horse gets on and stands still shut the trailer have the lead person go tie the horse and exit the trailer. Then go for a ride even if it’s around the block. Come back the barn praise the heck out of her back slowly as possible off and end for the day! You will need to do this all again and again every day till horse walks on with very little issue. Good luck if you have any more questions PM me on FB.