1. Similar
call numbers are grouped together, and they run progressively, in ascending alphabetical
and numerical order. An AC call number would be shelved to the left of
an AD call number; Q would come before QA; QA 75.6 would come before QA 76, and
so on. 
Books
are arranged on each section of shelving as though you were reading them on a
page of print--start at the top and go across the row, then down to the next
row, across the row, and so on.
2. The call numbers are read from the first line, alphabetically by letter(s), then by the second line's number, and then by the third line's letter and decimal number. The number on the third line is a decimal number, whether or not the decimal point is present. Although the call number in InfoLinks is displayed straight across, for example: BF575.F66 D83 1983, the call numbers will be displayed vertically on the spines of the volumes.
3. The fourth line of the call number may be a mixed (letter and number) term. If so, it is read in the same way as the third line-- by letter and by decimal number.
4. The fourth line (or sometimes the fifth line) may be a date, usually the year of publication. If all the elements of the call number are identical, the volumes are shelved in order of publication year. This is useful for distinguishing editions of a work or volumes of a journal.