In my story the two MCs will know each other from childhood, grow up together as good friends, have their own individual relationships, before coming together as a couple. I know roughly what I want to happen and when, the problem is how. what are some ideas that show the characters realising their feelings? If it helps, they are both loud and brash people. the boy is a bit obnoxious, and the girl is bossy and a bit of a diva.
Sooo many ways. One of my favourites is to show them suddenly being aware of things they took for granted. Like the other person's fragrance, or a mannerism - something physical. Dropping their name into conversations with other characters (mentionitis). Always thinking "oh, I need to tell X about this later, s/he will love it!"
Make them fight each other. Seriously. This is the best thing you can do with a romance. Before they realize they are in love drop something on them that absolutely forces them into conflict. This introduces, well, conflict. Both of them have to choose to win or to get the girl (as it were) and lets you play with expectations. You can make a woman who thinks winning is sexy; or a guy who finds he loves a woman who can really give him a run for his money. The conflict means that they aren't just a pretty face and some happy memories; they get tested and come through still loving each other and that says all you really need to say. In a literary sense, romance is conflict. If your book is going to make the romance a relevant part of it at all then the romance can't just 'work'. So set them up to fight, set them up to always be bouncing off each other and showing how much they love each other through their actions in resolving the conflict, not just by mushy dialogue. Conflict is sexy. Winners are sexy. Make them fight, make them have really good clawing at each other sex. Trust me. This is how you make a romance that is worth giving a damn about. When people just kinda flop into each other (both literally and figuratively) it's not something that's really interesting to look at. Only by putting them in a position where their romance is in genuine jeopardy is it something worth reading, with extra points for it being their own internal demons pulling apart.
I think a big fight between the two maybe. Then have a common foe come in and start trouble with them. Of course, they band together and defeat the foe. In the post conflict celebration, they realize that there are little quirks that they admire about each other. Allow him to brush a strand of hair from her face......and then.....it's on! Hope I was able to help