Here's a sample call number, with explanation for each line:
QE - indicates the general subject area; presented on the shelf in alphabetical order
862 - number line which indicates more specifically the subject area; presented on the shelf in numerical order within the QE section
.D5 - combination of letters and numbers that often represent the author's last name; presented on the shelf in alphabetical then decimal order
2006 - year of publication; presented chronologically on the shelf
Thanks to UCR and UMICH for these ideas.