In a great becoming a vampire fanfic, the character development is key. The vampire character should grow and change throughout the story. For instance, they might start as a cruel vampire but learn to be more empathetic. The world - building is also essential. You need to create a believable vampire world, with its own rules and hierarchies. And the conflict is necessary. It could be an internal conflict within the vampire, like the struggle between their human side and their vampiric nature, or an external conflict, such as a war between different vampire clans.