church visiting and dating

Last night I visited St Paul's Castle Hill. I really enjoyed it. They had a visiting preacher from the US, and the topic of the sermon was dating. Overall, I think he did a great job. Though I was left with many questions.
I approached him after the service and got his email addy. I'm looking forward to processing last night's data and then sending him an email with all my questions.

Many people say that you 'just know' when you have met the one.
So how do you know when it is the one? What is the X-factor?