on Live Write Thrive:

Many authors plan to write a series, but I’ve noticed when critiquing and editing novels that are part of a series, they often fail to keep in mind important elements that may not pertain to a stand-alone novel. Navigating through a series can be a kind of obstacle course, keeping focus through the many story developments to reach the finish line.

I’m not talking about a series of stand-alone novels that just feature the same character(s) but in different situations, such as in a mystery series showcasing a particular detective. In novels like those, just as with many TV series episodes, the plot is set up, developed, and resolved all in one book.

However, even in such series, you’ll often see characters grow and change. There may be long-term overarching storylines involving the characters that play out over many books.

There is no hard-and-fast rule regarding how to craft a series, but there are some things a writer should be careful to do.