For event clinics, I come prepared like I would to competition (minus the braids and show coat). My horse is as clean as I can get him, clipped, and in clean tack. Whatever tack I would typically use in competition is what I would use there, like martingales, bits, or jump boots.
Being neat and tidy in my horse's care and my attire shows respect towards the clinician and that I am taking his/her time seriously.
If your horse says no, you either asked the wrong question or asked the question wrong
And God took a handful of southerly wind, blew His breath over it and created the horse