Look up your books on your local library's website. Find the Dewey decimal number of your book and organize your library just as the public library is organized, by Dewey decimal number. You can record with pen and paper what the number range of a given shelf is, and when you want to find the book you look it up on your local library's website, find the Dewey decimal number and find the corresponding shelf.
Sort the books of your library so that they are organized by the first letter of the title. Then when you want to find a book, you can go through your library, looking at titles to quickly locate the book you want.
Sort your books so that they are organized alphabetically by the author's last name. Some people remember authors better than titles, and just like with titles, you can sort through your library quickly if everything is alphabetized.
Sign up for a website like goodreads.com, worldcat.org, openlibrary.org or librarything.com. These websites will allow you to create lists of all the books you have in your library. Your library wont be organized, but you will have a digital record of your books that you can use to track them.