History uses the perspective of time to explore the past and aspects of continuity and change.
The past trend in number of questions asked in Prelims clearly indicates that examiner is skewed immensely on history of Modern India and Indian National Movement.
Sporadic questions occur from ancient and medieval history.
Taking clue from the flow towards history of Modern India and Indian National Movement, you can consider giving more weightage to these areas when preparing for this section.
What to do?
NCERT books are quite useful in gaining knowledge and fact-sheets. For coverage of History of modern India, Freedom Struggle by Bipan Chandra is valuable.