Do I?

Lately I've been thinking a lot about what it means to like someone. Like how do you know when you like someone? In the past, when I decided to like someone, it was a conscious decision, like I would decide if they had the traits that I liked, and the chances of them liking me back, and I would base my decision on whether to like this person or not on those things. Last summer, I asked my cousin when do you know you like someone, and he told me that you can't stop thinking about them and you just know they're the one, like there's a feeling. I'm really unsure as to what this feeling could be, and if I've experienced it already or not. Also, I don't know if there's someone I'm always thinking of or not, because I think about a lot of people in a day. I do get warm feelings when I think of a "certain someone", but I actually don't think of him all the time. So this makes me wonder, do I like him? Is he the one? Because for me, I can only imagine myself marrying my first boyfriend, so I want to choose carefully, and make sure the person I like is a person I'm sure I will like for a long long time, as in the rest of my life, since liking someone means you want to be in a relationship with them right?