In some fanfictions, it might occur during a trip on the Hogwarts Express. They are sitting in a compartment, just the two of them. The train is chugging along, and the scenery outside is passing by. Harry looks at Ginny and starts a conversation about their future. Then he casually asks if she would like to go on a date with him when they get back to Hogwarts. It could also be after Ginny has been in some sort of danger. Harry is so relieved when she's okay that he blurts out his feelings and asks her out.
One scenario could be that Harry is really nervous when he asks Ginny. He might stutter a bit and his face could be all red. Ginny, on the other hand, is both surprised and happy. She immediately says yes with a big smile on her face.
One possible scenario could be that Hermione finally realizes her deep - seated feelings for Harry. In the fanfic, perhaps after a particularly dangerous adventure where they almost lost each other. She might approach Harry in a quiet moment, like in the Gryffindor common room late at night when most students are asleep. She could be a bit nervous but determined as she asks him out for a walk by the lake or a trip to Hogsmeade. This would be a huge moment for their relationship as it takes a more romantic turn.
Ginny asking Harry out could lead to a very interesting chain of events. It could cause some jealousy among other students who have a crush on either of them. Ron, for example, might be a bit taken aback at first but then come around to support his sister and best friend. As for their date, it could be something unique like a midnight stroll in the Forbidden Forest (with proper precautions of course), where they talk about their fears, hopes and dreams, deepening their connection.
One possible scenario could be that Hermione is initially shocked. She might have been expecting someone else to ask her, like Viktor Krum. But then she realizes that Harry is being sincere. She could accept his invitation, and they start preparing for the ball together, sharing nervous laughs and excited chatter about what they'll wear.
One possible scenario could be that they are in the Gryffindor common room. The fire is crackling, and everyone else has gone to bed. Harry and Ginny sit on the couch, and slowly start to get closer. Their eyes meet, and then they share a gentle kiss that gradually becomes more passionate as they let their feelings for each other take over.
They might get married and start a family right away. In fanfiction, it's common to see them settling down and having kids, living a peaceful life after all the chaos of the battle.
Maybe they go to a wizarding cottage in the countryside. They explore the nearby magical forests together, discover new magical creatures, and Ginny could teach Harry some new Quidditch tricks in the large open fields around the cottage. And of course, they have cozy evenings inside, cooking together and snuggling up by the fireplace.
One possible scenario could be that Harry needs Hermione's help with something specific in Hogsmeade. Maybe he wants to research a certain magical item in one of the shops there, like Zonko's Joke Shop for some prank - related research or Honeydukes for information on a particular sweet that has a magical property. He knows Hermione is the best person to go with as she's so knowledgeable about all things magical.
Perhaps Harry asks Padma for help regarding his date with Cho. He's all confused about how to make Cho happy at the ball. Padma, being a girl, might give him some useful tips. Like she could tell him about the kind of flowers Cho might like or the type of music she enjoys. This would show Harry's vulnerability and his attempt to make his date a success, while also creating an unexpected bond between him and Padma.
One possible scenario could be them renovating their home at the Burrow. They might be adding new rooms for their future family. Ginny could be using her magic to make the place more cozy while Harry helps with the physical labor, like moving furniture with a levitation charm.