In India, what they teach in English class at school level is all blah. In the high school, they must focus on sentence-writing skills, something the teachers don’t pay attention to.
Indian students, unfortunately, become obsessed with vocabulary (I mean difficult words) and later with ideas, but have little knowledge about how to use the words and ideas in an effective sentence.
The Art of Styling Sentences is a great book. I have studied it chapter by chapter and exercise by exercise. The book and its drills would do wonders to you if you work on them studiously.
Some other books will also help you in writing effective sentences: Style: Ten Lessons in Clarity and Grace is one; and Don Killgallon’s books on sentence composing are other brilliant textbooks. This book definitely makes its own space in the shelf along with those written by language profs of American universities. Don’t look down upon this because it is brought out by the company dominating the professional test-preparation market.