How can I write a good Eragon, Arya, and Lemon fanfic?

First, do your research on the original Eragon series to understand the characters of Eragon and Arya well. For the lemon element, you could give it a symbolic meaning. For example, it could represent purity or a new beginning. Then, create an interesting plot that weaves the three together. Maybe start with a simple situation like Eragon giving Arya a lemon as a gift, and then build from there.

Well, start by coming up with a unique concept. Since we have Eragon, Arya, and a lemon, you could make the lemon a key element in a magical mystery. Let's say the lemon has a hidden message inside it that only Eragon and Arya can decipher together. Develop their personalities further as they work towards solving this mystery. Also, use descriptive language to bring the world of Eragon and Arya to life, and make the lemon seem like an integral part of this world, not just a random addition.