How do you find the ISBN number of a book?

How do you find the ISBN number of a book?|||If you check Amazon or Barnes %26amp; Noble, they have that information. It is also on the library catalog and on the back side of the title page. It is often on the back cover of the book as well.|||It's usually located somewhere near the barcode.|||It's on that front page with all the small print that lists the author, publisher etc.etc.etc.