I am a logical person and for me there is nothing like falling in love, that is just nonsense.
However love is an emotion, a feeling so falling in love is also connected to your feelings, it starts with one person getting attracted to another and then it turns into developing trust and strong emotional connection with the other person. When trust and emotional are at their highest/strongest/deepest at that point that is called love.
This entire process can happen over lots of dates, or it can take weeks, months to happen as well.
It kinda just... happens. Like, you're just going through your day, and maybe it's something the other person does, or says, or maybe it's something completely unrelated to them, but it just suddenly hits you that you're in love.
they see a cute girl consider sex, if yes, consider relationship, if yes, consider marige, if yes, consider life with that person, if yes, fall in love, if no to any of these things then there is no love.
When you know you've found the one. Trust me I'd know... when it happens
We meet a girl, we date her for a while, with a few to seeing if she's a suitable long term partner. We discover she is. We get serious about her. We gradually discover she's better than we thought. Better than we imagined. Better than we think we deserved. And by then we're in love.