You start out as friends. Two people who like to do the same things together. And you continue to be friends - continue to like to do the same things - spend time with each other doing those things and have a good time.
Simple as that!
My wife and I had a ‘love (at least, interest) at first sight’ thing that happened, though some drama occurred before we got a chance to act on it!
We met in university, in the university pub as a matter of fact. I noticed this very hot woman in the booth next to mine, but she was with some guy, whom I assumed was her BF, so I didn’t introduce myself. Actually, it was he who introduced himself to me - he was interested in some work I was doing (I was sketching out an album cover for a friend-of-a-friend’s garage band); we got to taking, and he introduced me to his friend, the woman I had noticed. We got on so well, talking about music and stuff - he invited me to come out with his buddies to listen to some live Jazz.
When I went, the woman I had noticed earlier was there as well, and I finally got a chance to talk to her - and we were flirting outrageously. I was kinda wondering if she was his GF. He seemed to act as if he was, but she seemed to act as if she wasn’t, and I didn’t know them well enough yet to simply ask outright. [I learned much later that he wasn’t but wanted to be - she had no interest in him other than as a buddy].
That’s the last I heard from him, and I figured it would be the last I heard from her as I had no contact details for her and only a slight acquaintance. However, a couple of months later, after I had totally forgotten about either of them - she calls me out of the blue, to invite me to a party at her dorm. I was surprised, and pleased; so I made her a little gift - a spider made out of modeling clay, with a crystal from a broken chandelier for the abdomen - and hung it over her bed when I came over. The party lasted most of the night, and I stayed over; after that we were an item, and now, we’ve been married for over 20 years!
She told me the rest of the story some time later: what caused her to call was a coincidence. A friend of hers was, by random chance, someone I sat next to in a class - another very pretty woman. Apparently, the two of them got talking, and this other woman brought up my name. She asked whether she (this other woman) ought to invite me to her dorm party. My future wife said she knew me slightly, and that she thought I was “too weird” to make a good BF for this other woman - so that other woman, taking this advice, didn’t invite me. That night my future wife invited me to her party instead. Allegedly, this other woman, when she found out that the two of us were now an item, having been invited to my future-wife’s party, was furious; my future wife said she had no cause to be annoyed: “I was totally honest in my advice - you are too weird for her. But not too weird for me”.
Ah, University relationship drama. 
it starts how it starts - a glance, a smile , maybe with a sandwich.
But once it starts - it starts - and there is little use in denying it.
First you get a Russian Bride magazine and pick out the hot one and find out if she is available. If she is not go on to the next hottest one and so on.
It should start with your choosing to sit at a campus dining room table occupied by a woman who yells at you for reading a magazine instead of talking to her.
Worked for me, anyway.