When do you tell a girl that you want to be her boyfriend?

So I met this girl that I like and we are going to go coffee, and I was wondering do you tell her on the first date that you want to date her or a little longer. I was talking to a friend and she said that you need to wait till the third date but i think that is too long, I have been out of the dating scene for a while but usually we decide mutually after the first date. Also when I do decide to ask her how do I ask her.