One of my stories has a romantic subplot where two people that have been friends for a long time (on and off) realise their feelings about each other and start to date. Furthermore, I want the male character to negotiate them getting together. Maybe because I'm not very experienced, but I have no idea what plot points you'd use as a vehicle to get from point A (friendship) to point B (romance). What do you use to start a romantic arc, when it's not exactly love at first sight?
Is it a full-on friends-to-lovers, or has there been mutual attraction between them all along, but they haven't expressed it for whatever reason? Assuming it's full-on, I think you want something to trigger a character seeing the other character in a new way. Maybe one of them starts getting serious about someone else and that makes the other character realize what s/he stands to lose. Maybe one of them does a "makeover" and becomes more physically appealing. Maybe they have a big fight and the friendship seems to be over and they realize that they're losing more than just an ordinary friend. Whatever. Something triggers. And then traditionally there's some denial on one or both parts, some resistance to the idea, some fears that getting romantic might ruin the friendship. They eventually get physical, to whatever degree, and it's kind of weird and awkward and they pull away for a little bit but then realize they really, really miss the other. Shazam! Friends to lovers!
"Sincerely, Carter" is a great book in this genre. I recommend you to read it. Maybe it will help you to improve your writing. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- Essays on literature
If I wasn't sure, I would personally try applying the Heros Journey to arcs like this. For example, them being friends represents The Ordinary World, denying their feelings being Refusing The Call, accepting their feelings is Crossing The Threshold, and final "We're officially together now" moment would be Seizing the Reward, etc.
Following Bay's advice, one scenario I've seen is that the triggering event is when one of the characters is at risk of being removed from the other character's life - not only as she points out by becoming interested in someone else, but potentially moving far away, switching to a different job/industry (if they are workplace buddies), etc. There's a pattern, in genre Romance at least, where it turns out that one character is taking the other's presence for granted, and only when presented with a loss of that do they realize they have romantic feelings. I recently read Scoring Off the Field by Naima Simone, which followed the above scenario almost exactly.
I'd say the first hint is how often people spend time together and how bad their excuses for it are. For example, asking if they want company to run a simple errand. As someone who's dated friends, I hope this will be helpful. I'd been friends with them for a while when I first noticed the sparks of attraction. Thought about them often, missed them when we were apart. It turned out the interest was mutual, so we began spending more and more time together by trying to match and merge our activities when possible (e.g.: I had to visit and write reports on some touristic sites, he had to draw from observation, so we'd visit sites together and I'd draft my report while he was drawing). Once we got together and people felt comfortable saying "I knew it!" to my face, they'd point out how often we hung out, texted, mentioned one another.
