If you're the kind of reader who doesn't like doing damage to their books - who wants to keep them in pristine condition, look away now! But if you want an extremely easy and visual way of remembering what you've read - and developing your creativity by quickly looking up those ideas again - I found this is the best way to do it.
  The more ideas a book can give you, the better the book becomes as a resource.
That means you can recommend it to others, or simply identify the book is a great source of information.
But you need to find a way of showing how many great ideas this book provides.
You simply need to mark the page which has information that appeals to you.
There are many ways to do this.
Some people put post-it notes on the page so they stick out.
Other people will put in bookmarks.
While these are a good idea and they are certainly nonintrusive if you are borrowing the book, they don't easily show how many ideas this book contains.
I use my system this way with my own books.
Every time I come to a page with an effective idea on the page, I turned down the corner of that page.
In other words, I "dog-ear" it.
After I finished the book, I can turn the side to face me and count the number of pages I turned down.
If there are a lot of those, that book is a keeper.
And when I'm looking for creative ideas on any subject, I quickly check the number of turndowns in each of the books I'm looking for.
The one with the largest number of dog ears is the one I can generally get some good ideas from without much trouble.
Try it!