Player Warning!

When making a PC, there are some general rules to help make a fun PC.
1. What type of story do I want to see?
What do you want to experience? What kind of arcs do you want to put your character through? You are essentially able to create a main character of a story, so might as well pick your genre.
Perhaps you want to experience the feeling of discovering mysteries, perhaps you want to experience the thrill of combat which also comes with the maintainance and preparations beforehand. Maybe you want to experience the rage of a vengeful person, and the satisfaction and loss after exacting said vengeance.
Whatever the case is, have an idea of where you want this character to go.
2. Self-Motivation
Your PC is in this party for a reason. Have your PC be self-motivated to adventure and be involved in situations. Whether it'd be due to their own personal code, a stigma that they follow, perhaps seeking a thrills and dangers, this sort of links to tip 1. Whatever the motivation, it will usually be linked to the story you want to experience.
3.  Party Chemistry
Your PC should be in the party for a reason. If that PC could be replaced by just anyone, then its a bad PC. Have the PCs made together, talk with one another about their group dynamic. The PCs should generally stick together for reasons other than 'the DM said so'.