The best thing you can do for yourself on a bookshelf, is sub-divide. Luckily, there are many different ways to do this and you can customize it to the space (and the bookshelf) that you have. The easiest way to subdivide your books is to use different shelves for different categories. You can also use a bookshelf like mine that is already sub-divided for you.
If you don’t have the ability to have a physical space difference, get creative! You can use bookends or little trinkets to manually separate the book sections. When it comes to the types of sections you use, it completely depends on the types of books you have and the way you think about them in your head.
Due to the recent prevalence of electronic readers and my severe dislike of hoarding things, I only have two book categories. One is the books I am waiting to read and the other is the books I would love to read again.
Don’t get me wrong, I LOVE books and always have. There is a stack on my nightstand of the books I’m reading right now (I’m always in the middle of more than one – different genres for my different moods). I also always have a donation pile of books in my donation area. If I’ve read a book and know I’m not going to read it again, I donate it to the library. Books shouldn’t just sit there; someone should get to enjoy all that they have to offer! My grandmother has a book goal that I love: when she dies she doesn’t want many books in her house. If she loves it, she wants to pass it on to a friend or family member that she thinks will enjoy it. If not, she donates it. This is a perfect way to make sure all books stay in use!
For young children, who tend to enjoy the same book over and over (and over and over and over) again, it is a good idea to divide the books by how long it takes to read them. For example: short story, long story and chapter books. As the children get older, the categories should shift to the reading level. This is often done by grade level, but can also be done by age or even by specific child name.
For adults that enjoy a large library in their home, divide the books by genre. You know I love labels for everything around the home, so if they work for you, label the areas underneath each section!
Placement of books on a shelf completely depends on your goal: aesthetics or function? Personally (mine is in the living room) I go for aesthetics. I always arrange the books from tallest to shortest from the outside in. I also know people who like to arrange items by color, this can look really nice as well!
If you’re going for functional, the key is always alphabetical within each category. If you are good at remembering author names, that is the alphabetical system used by most libraries. If not, then go for real functionality and arrange the books in alphabetical order by title within each section!