As you walk through the library, you will notice that shelves are labeled (images below). These labels will tell you which call numbers are located within a specific row/aisle. Rows are organized by LOC call number, alphabetically, going from the left most row to the right most row. The beginning of the alphabet starts on the main floor of the library and ends upstairs.
Call numbers are on (or near) the spine of the book. The call number is made up of a combination of numbers and letters that are read left-to-right, top-to-bottom.
First letters: one, two or three letters that are arranged alphabetically. So K comes before KF which comes before KFD.
First numbers: the first set of numbers are read as whole numbers. So K5 precedes K23 which precedes K452 which precedes K1298.
Second letters: are preceded by a decimal point and are arranged alphabetically. So .B comes before .L which comes before .M.
Second numbers: are treated as decimals. So .33 comes before .813 which comes before .9.
There may be another letter number combo. If there is these numbers will be read as decimals as well.
Year: If there is a string of four digits at the end of the call number it usually signifies the year and should be read as a whole number.