Lifehack: Label your books with Dewey numbers

I've tried again and again to come up with a system for organizing the books on my bookshelf -- put the computer books here on the left, fiction here on the right, reference books on the second shelf ... but after a while I would forget what book goes where. Or a certain topic area runs out of shelf space and I don't know where to cram in new books.

Well, the problem of classifying books was solved long ago by librarians. The Dewey Decimal System is a popular system. Using my trusty automatic labeller, I labelled each of my books with the Dewey number (gleaned from the Library of Congress and the Vancouver Public Library websites). Now when I put a book back on the shelf, I don't need to think about where to put it -- I just shelve it according to its number (for example, Seven Habits of Highly Effective People is 158, Getting Things Done is 646, etc.)