Writing Corner: How I Write - Keeping Track of Multiple Books Across a World

When writing multiple series set in one world, keeping track of details can become difficult, especially if the main characters in one series are secondary characters in another.  My process for keeping track of events, timeline, characteristics, and conversations is old school.

Basically, I open all of my previous books as pdfs (easy to toggle to and not so easy to accidentally type over).  I have a rough idea of which book holds which details, so I can quickly flip to the pdf and search for a word or phrase and reread the passage.  

I also keep a written world bible filled with characters in each book and their relation to main characters and each other.  Did I meet a police officer from such-and-such, can I use them again in later books?  What about mentions of friends and family members?  Places that characters grew up?  Etc.

For instance, I have several police characters that my main character in Touch of Gray interacts with in the first book.  I had a vague idea that I would revisit them in a future book, so I wrote a little note to myself about possible future plots.  In fact, I have the next five books with vague plots and featured characters.  Under the characters, I list previous books they've been in and key characteristics to keep them consistent between books.  

Under plots, I jot an idea that sparks in me while I'm writing a current book.  Then I can expand on it as I write, or I can change or adapt it to my current plot.  Often, I incorporate a future plot in my current writing, planting seeds of future plot as I go along.  This is why I prefer to write at least two books ahead of publication, in case I need to go back to the 'current' book and tweak a detail to more easily fit a future book.

But another police character from the first book was just an interaction on a phone call and I had no intention of revisiting them.  Imagine my surprise when I found myself writing an offshoot series and setting it in the geographical area where this police character dwells.  I could now dust off this character rather than create a whole new character.  It works pretty well.

Regarding timeline and location, I keep track of my characters on a master calendar.  This way I make sure to correctly address where characters are located as often, their book timelines overlap.  Location wise, there is location in other area, i.e. geographical location.  For geographical layout of the main location (in this instance, Albuquerque), I've created a map of the area.  This is the main character's house, here is the worksite, here is best friend's house, here is police headquarters, etc.  I find it easiest to have a concrete image to refer to rather than store it in my imagination.  It is easy to get turned around in my head, so I sketched it then scanned it into an image for easy reference.  I am a bit too nitpicky for drawing directly on my computer, so pen on paper works better for me.

Keeping past character and plot lists, plotting out future books as I write current books, and having a master calendar and master location map is how I keep track of multiple books across a shared world.  How do you?