Read the call number from top to bottom. Start with the letters at the beginning. These are in alphabetical order:
A, B, BF, C ... L, LA, LB, LC
The letters are followed by a number. Sometimes these contain a decimal:
1, 2, 3, 45, 100, 100.12, 100.13, 101, 1000, 2430...
Next will be a decimal point followed by a letter and a number. Read the letter alphabetically:
A, B, C, D...
Read the number as a decimal:
.B833 = .833 is before .B84 = .84
Some call numbers end with the publication date. Read in chronological order:
1985, 1991, 1992...
If your book is part of a set, its call number will be followed by the volume number.