One should form a group of 4-5 people, as the preparation for Personality Test cannot be done in isolation. Try holding as many mock interviews as possible.
No training institute can develop/transform your personality in a few days. However, some of the tips may help in ironing out some weaknesses/gray areas and can provide an avenue for a well-planned preparation and group discussions.
Take mock interviews with your friends. In the mock interview, ask your friends to grill you so that you can face pressure from the Board easily.
Discuss a lot with your friends. This not only helps in you assimilating different points of view, but also enhances knowledge levels.