The only way to make sure someone was surprised is to see their reaction when it happens. That sounds weird because it’s obvious that the person would be surprised, but you never know whether or not they were faking it. So how do you know if they were surprised or not? It’s a very simple trick: surprise them with something very small before the actual big surprise. Like randomly get the person something and not on a special occasion of course. Then note their face when they see it. It won’t be the shocked face you’re looking for, but it will be the face you’ll be seeing after the actual surprise. You’ll see the eyes and the smile of true content. It’s at that moment when you will know what the element of surprise is. It’s impossible to forget the face of a surprised person. That, I am sure of.