You cannot prevent certain normal growing pains. Not every kid will throw a tantrum, and a kid throwing a tantrum is not always an indictment of your parenting. Your job as a parent is to raise a healthy, intelligent, responsible human. Somone who can think for and take of themselves. You should always be calm and rational with your kids. Sometimes discipline or even punishment is needed to correct bad behavior, but never do it in anger, and try to make it constructive. For a tantrum in particular just don't give it any fuel and it burns out almost instantly. I wouldn't even acknowledge it beyond just instantly picking them up and going home. My general opinion is that if you can't behave in public then you're going home, and if you throw a tantrum there won't even be a discussion anymore - your opinion on the matter is no longer relevant. It usually only takes a single time because it's a shameful experience for the kid if you don't match their emotional intensity and remain calm.