Your Horse People use all sorts of methods to make their selections and place wagers. Some people pick the horse in the race that has the best winning record.
Some people even choose by the post position number.
All this information is available in the program you get as part of your admission fee. To the surprise of many, betting on thoroughbred racing is not like betting at a casino. You are not betting against the race track to try to win. This is pari-mutuel betting. That means that all the bettors are betting among themselves.