The best way to get good marks in the General Knowledge section is by reading more and more. You can read newspapers, journals, and magazines to stay up to date with the latest events.
You can also increase your general knowledge by socialising. Discussing social topics with your friends and acquaintances will help you clear your concepts around those topics. You can also have conversations about the major events happening in the country as questions may be asked pertaining to those topics.
You must be acquainted with ancient Indian history, capitals of every country, important dates in history and Science, Sports, awards and honours, and books and authors as questions may be asked from these domains.