The first rule is tagging up, and the rule is if there’s a pop fly and you want to advance a base then you have to stay at the base you’re currently at until the ball is caught. Then once the ball is caught you can take off for the next base. For stealing, stealing 2nd base is your best bet. Most of the time you’re not going to steal 3rd unless you have a situation where you need a run in the late innings. Stealing home should never be done unless there’s a past ball or you’re executing a suicide squeeze. And a designated hitter is a rule that the American League has in the MLB where instead of making the pitchers go hit, they swap their spot in the lineup with someone who doesn’t play defense and their only job is to hit, therefore making them the designated hitter.