Originally Posted by J Hussain

Well it depends on where you live. Lahore is known as the intellectual capital of the country and that holds well in case of CSS coaching classes. Kindly mention your location first so that academy/teacher can be referred accordingly.

Don't overburden yourself with too many books. You can have idioms book of McMordie. It's important to practice writing and get your work evaluated by an experienced English teacher.

Good'luck!