How to Write a Long Running Series

Many listeners want to write a long running series, but it can be difficult. So what are your tips for writing a long running episodic series? I think definitely start off with characters that you yourself feel strongly about, em that you want to explore. It's important to know when a character has served their time. And i did do something in book which has caused a lot of bloggers and reviewers to say they'll never ever forgive me.