Okay so I am going to have to load my horse for the first time in a trailer he doesnt know without his buddies tommrow. And I am so stressed out about it because the one time I tried to load him in an trailer he didnt know he wouldnt get in it

I have no idea what kinda of trailer it will be. Does anyone have any tips on loading a difficult horse?
Also I am doing this tommrow and have had no time to practice let alone a trailer to practice in...i am going to start practicing for future trips when I get to my new barn.