Generally, top practising firms (eg. Mehta & Mehta) will harass you a lot by asking difficult questions. You will need to have a good grip on sections and legal updates. PCS firms generally ask simple questions on Meetings, directors, Sec 372A, Sec 77A, Incorporation of Company, change in name, change in registered office address, Change from Pub ltd. co. to Pvt ltd. & vice versa etc.
In Companies, generally, you will be asked 1 or 2 extremely simple questions on Company Law and later they will ask like " Tell me about yourself ".They may even ask you about your study.
If you can not answer the questions in the interview do not get nervous, as all students are in the same boat, just be confident !
Best of luck !