One of my friends graduated from NLSIU and here are the things I got to know from him. It could be considerably tough and you might not get what you expect.
The most important thing is to know the syllabus. Then go through the current affairs. Solve the maths portion from the previous paper.
Don't read GK from Lucent, Arihant, and don't read history. In legal aptitude, the most important thing is the previous year's question.