I am writing a series with five books in it. There are times I think I’m going crazy trying to keep all the little things straight. So I made a spreadsheet with each character, noting physical and emotional characteristics as well as what they drive, where they live, any pets, etc. But not only do you need it for the characters, you a spreadsheet or a written document about the places your characters will visit in the town the series is placed in. You need to keep track of street names, landmarks in the area. All these things can be in any of the books and need to be the same. Learn from my mistake. Start this from the very beginning of the series, not book two.
Also, when naming people in a book even someone you don’t think will appear in any other book, give them a name you like and won’t mind writing a whole book using them as a hero or heroine. You never know when one of those “throwaway” characters will become your next hero or heroine.
