Well, start by researching about host clubs if you're not familiar. This will help you add authenticity to your fanfic. When writing the relationship between the reader and the host, start slow. Let their connection build gradually. Use vivid descriptions to bring the world of the host club to life. For the characters, think about their motives and goals. The host might be motivated by money at first but then truly falls for the reader. And for the reader, their goal could be to have a fun time at the club but ends up finding love. Add some sub - plots like the reader making friends with other club staff to make the story more complex and interesting.
To write a great Best Host Club x Reader fanfic, you need to focus on the emotions. Make the reader feel what the characters are feeling. For example, when the host flirts with the reader, the reader should feel a bit flustered. Include some conflict too. It could be internal conflict for the reader, like whether they should fall for a host or not. And don't be afraid to add some humor. Maybe the host makes a silly mistake while trying to impress the reader. Plot - wise, make sure there are enough twists and turns to keep the reader engaged.
First, create interesting characters. Develop the hosts with unique personalities and quirks. For the reader, give them a relatable backstory. Next, set the scene well. Describe the host club in detail, from the decor to the atmosphere. Also, build a good plot. Maybe start with a simple encounter between the reader and a host and then gradually develop their relationship. Use dialogue effectively to show the chemistry between them.