The question "where next?" is even more relevant for those who write single books. (Or even if you write a series but plan to use different characters as the "leads". The Discworld series by the late much missed Terry Pratchett is a good example of this)?.
Thinking of literally where, is the physical place where your characters were born, live etc of relevance to the way your character thinks and acts? How best to describe your world is worth taking your time over as you want to plant the "right" impressions in your readers' minds.