Read Read and Read
G.K. Is a very unpredictable section. 1)Read the Hindu or any othernewspaper
You have to start reading newspapers. The Hindu is of great aid. It increases your vocabulary and gives you unbiased opinions, Something that will be of great help while writing answers.
2) Read and understand NCERTS of History, Geography, economics and Political science from grade 5 to 10
This is something very basic however it helps to a large extent in preperation