Feeling/being in love, for me, is not sexual at all, nor is it related to looks, nor can it be sparked by social scripts. I cannot fall in love at first sight if the person isn't doing or saying anything. I cannot fall in love from someone buying me things or taking me to fun places or giving me compliments or making me laugh or sharing my hobbies or making me feel like the center of their world.
What makes me fall in love? Feeling a mutual excitement at the understanding and growth we are creating together. Feeling that they are as excited about my ideas and experiences as they are their own. Feeling them be fully present with me, especially when it's because they are so engaged with my presence that other things fade out (not including chronic pain/depression/etc). Feeling a strong desire coming from them to know me balanced by a strong desire from them to be known coupled with a strong self-awareness; especially when they take opportunities to self-examine in front of me, without forgetting me. Feeling a vibrant connate resonance about them enacting/embodying one or especially more of my core values: justice, respect, compassion/connection, wonder/reverence, curiosity, transparency/openness, honesty, thoroughness, creativity, imperfect action, growth/change. This can happen in so many ways. Examples: they describe how they engage in justice work, they show respect to someone who usually doesn't get it (like a child), they describe a connection they have, they respond to an expression of wonder with an equal level of enthusiasm, they ask prying questions or wonder aloud about something your average person takes for granted, they share something vulnerable and self-aware, they tell the truth when it makes them uncomfortable, they make sure to be complete when doing a task, they customize items they use daily, they take action when it is needed even though they are clumsy at it, they describe things they've learned and how they've applied them to their life... Many many possibilities here.
Feeling in love can also be squelched by violating one of my core values. If you are unwilling to devote spare resources to creating justice, show lack of consideration for how you affect others, show apathy to suffering, react to wonder with dismissiveness or indifference, don't question yourself, respond to questions without thought or depth, lie, are sloppy in tasks done for others, act like skilled technique is the key to art, refuse to take a helpful action because it's not the perfect solution, or think that staying the same is good, any feelings of in-love I have for you will be diminished. That also has many possibilities. Often I will feel a swell of in-love for someone and then five minutes later that will be burst; for instance I'll notice their carefully and meaningfully decorated music case and feel very in-love, and then they'll talk about all these 'poser' musicians who don't do [some specific technique] and that feeling will be completely dissolved.
I also can feel in love without it being a constant state: I have felt in love with people for a moment or a day, or constantly over a period of years. I often feel in-love with people, but I don't describe it as 'being' in love unless it is mutual and consistent, something that I see continuing indefinitely. Usually it goes from a feeling of in-love-ness to actually being in love when we deliberately create the space for that, or when the space is accidentally created through just spending a lot of time together, or when they express the same feeling and a desire to explore/deepen that feeling.
When I am in love with someone as a state of being, I feel a continuous strong desire to be close to them. I feel like I want to know every meaningful thing that goes on in their lives, I want bring them joy, I want to help them grow, and I get easily overwhelmed with how wonderful they are and want to talk about it all the time. I want to kiss them, hug them, and touch them in ways that feel good to them. I think about them often and miss them when we have not connected in an unusually long time (for us: this can be a few hours or a few weeks). I want to give them presents if I find things they would like. I want to help them with tasks that they find difficult or stressful. I want to share meaningful places, art, and media.