Don't just plug numbers into formulas. Read the first 5 pages of Chapter 1. Understand the difference between a parameter (population) and a statistic (sample).
Miraj Mirza does something brilliant: He solves the same problem multiple ways. Grab a notebook. Cover the solution with a paper, try to solve it yourself, then reveal the answer.
For students needing extra help, solution manuals for both Part I and Part II are also available. Introduction to Statistics - M. Afzal Beg, Miraj Din Mirza