Well, since we are both fellow Slytherin fans, I will help you. So, usually you don't wanna tell people you have a crush on them, or at least that's what my Aunt says. You have to grow that attraction. You have to smile a lot at them, but not too much or it's just creepy. You have to talk to them and be nice. Then, once you know each other better, you can ask them out or something. I've never had experience, though I'm trying to follow these steps with my crush. I'd love to hear what he said!