This book is a reference book for the researchers working in the area of 'Optimal Stopping Rules'. It provides a foundation and comprehensive background of the optimization technique used in optimal stopping rules popularly known as "Secretary Problem." To provide simple algebraic treatment for solving the secretary problem and some of its extension is the primary objective of this book. There are many variations in the original secretary problem. In this book we focused only on the algebraic treatment and that too with only one important variation namely 'Two Tailed Secretary Problem'.