I quite often ride horses I have never ridden before.....I am riding one today. I may ride it to clock bush miles on it for someone, to try and help sort some issue out, to compete on the day*#) or just to get another notch in my pony riding gunbelt. If I have access to a round yard I prefer to throw them in there and chase them up a little bit, putting pressure on and taking it off to see how they react. I then saddle them do a few ground work bits and pieces especially work out if they understand the side yield for a one reiner and then jump up. If they are a real unknown quantity I may lay over the saddle and get someone to lead them forward and see if they hump up. I also get as much information as I can about the person who knows the horse. When it comes to 'what do they wrong' .......... I don't mess about with niceties basically you be honest with me and tell me what the horse did to dump you pet.......lets all be honest here. My interrorgation method is very well honed and extremely effective. So what do you do before you leap aboard a pony you don't know?