To find a book in any library, you must have:

• the call number
• the location
• the loan status

The call number is the actual number that is on the item, and provides the clues to find the item in the library's arrangement. The arrangement may be in the Library of Congress Classification System, or the Dewey Decimal System, but there are literally hundreds of different arrangements, many unique to individual collections.

Just as important is the location. Most libraries have their collection broken up into sub-collections. So, there may be a reference collection, a special subject collection, many items may be in storage. All but the tiniest collections go into more than one room. So, to find a book, it may be in a special area. The catalog is supposed to supply all of this information.

Loan status
You may still experience problems if you are in the correct location, you have the correct call number and you see the correct place on the shelf, and the book is still not there. This can occur if someone else is using the book. When someone has checked it out, the record in most modern library catalogs will tell you if it is checked out, and when it is due back into the library, so you always need to look at the catalog record. (Remember that you can always place a hold on the book)
If it has not been checked out but is not on the shelf, someone else in the library may have used it. Look on the tables, and on any special shelves designated for leaving unread books. It may also be in another room.

If you still cannot find it, tell someone at the front desk. We may be able to find it someplace else, or we may have to search for the book if it has been misshelved.