I think you need to focus on the characters and their relationships first. Then, come up with an interesting plot that fits the theme of the original story.
One popular theme is the further adventures of Hiccup and Toothless. Writers often explore new lands and challenges that they might face. For example, they might encounter a new type of dragon with unique abilities.
Well, when Hiccup is a dragon in fanfiction, it could be because of an ancestral connection or a mysterious experiment. This could open up new storylines and allow for exploration of his identity in a completely different way. Maybe it's a way to show his ultimate empathy and unity with the dragon species.
Hiccup in the fanfiction typically trains by forming strong bonds with the dragons first. He shows them kindness and respect, and then gradually introduces training exercises that are fun and challenging for both him and the dragons.
Hiccup would likely approach it with enthusiasm. Since he loves his dragons and his adventures, he would be eager to see how others imagine the world of 'How to Train Your Dragon'. He might find some fanfictions that give him new perspectives on his own life and relationships. Toothless, being a dragon, might not understand all the words but would react to the emotions in the stories. If the fanfiction shows a happy moment between him and Hiccup, he might get excited and start making his little happy dragon noises. Astrid would probably analyze the fanfiction carefully. She would look for any inaccuracies in how her character is portrayed, especially when it comes to her skills as a dragon rider and her relationship with Hiccup.
One possible reaction in a fanfiction could be about the new dragon species introduced. A character might be in awe, thinking 'These dragons are so unique! Their colors and abilities are like nothing I've ever seen in Berk.'
Zephyr fanfiction in the 'How to Train Your Dragon' universe offers a chance to explore new adventures and storylines for fans. It allows for creativity and imagination to expand the existing world.
There are some great fanfics that focus on expanding the relationship between Hiccup and Toothless. One I like is 'Dragon Bonds' which delves deeper into their friendship.
The main technique for 'How to Train Your Dragon' fanfiction is to immerse yourself in the universe. Know the rules, the magic, and the relationships. Then, let your imagination run wild while keeping it somewhat grounded in the original framework.