If you have him in a fitted rope halter that he can't worm his way out of, try a bucket of hay? My horse wouldn't tie and so I would give him hay and then sneakily tie him to a piece of bailing twine attached to a post. Over time, I took the hay away and he was happy to stand.
The key to any new thing is to do as much as you can, without him reacting. So if you manage to clip him to a crosstie, leave on for 1 second, BEFORE he reacts... or fusses.. or whatnot, and then take it off (give him a release.)
EDIT: I reread a few responses and I see what's going on. He needs a better halter. Making it tighter doesn't teach him anything. Put him in a fitted rope, and you'll have no problems with him escaping it. Nylon web will break.. my horse in the past could weasel his way out of his. He'd rip the crossties and the halter apart before he decided to stand. I put him in rope (and it was a big gauge fluffy rope..) and NO problems. He couldn't escape from it, couldn't break it. I kept him in rope, have had no problems since. Now I can put him in leather and he's happy or I could put him in nylon (if I wanted to, not a fan of nylon) and he's fine. He ground ties, cross ties, post ties, tree ties, toddler ties, whatever.
But it helped him putting on a rope halter and giving him a bucket of hay (he was a nervous horse.)
"Strength is the ability to use a muscle without tension"
Last edited by Skyseternalangel; 01-19-2012 at 04:47 PM.