Warning: I may get somewhat technical later on. However, I will try to keep this post so that everyone can understand it.
Some books have small casts–of maybe around fifty characters total. Then there's others, with larger casts, maybe 200 total characters. And then there's the Lord of the Rings, with millions of characters.
Okay, maybe not millions. But it does have a lot.
If you're writing a book with a large cast (or even one with a small one), you will probably want to have a list of your characters.
What I've done, is to create a spreadsheet in MS Excel, with one row for each character. This has: their name, their age, rank, occupation, species, height, other names which they're known by, year of birth, affiliation (protagonist/antagonist), importance (main character has 0, minor characters have increasing numbers, I go up to 5), year of death, and 'Dead?'.
This means that if (when writing a later book in The Arboreal Shadow) I have a character visit any given city, I'm not going to make up an elder for that city, only to realize later on that the elder (a different person, though) was mentioned in the first book.
Several of the columns, though, I don't edit. The 'Age' column is calculated using the 'Year of Birth'. The Dead? column is a special one, which says Yes if characters are dead, No if they are alive. This is calculated by checking if the current year (which is specified somewhere else in the spreadsheet) is after or before the year that the character died (or will die).
(Click on the photo to get a larger view.)
The characters can be sorted by any of the options – you can show all characters in order of age, or in alphabetical order by first name, or by species.
I've found this character chart to be useful. If you'd like more detailed instructions on how to make it, then say so in a comment and I'll see if I can help you.