My first advice to You is dont prepare for the sake of interiew, you should get that by experiance in the projects you are working on.
I normally ask this question in interview to the persons having 1 to 3 years of experiance. 1. Name any few methods that all the classes have in common ? 2. Whats the difference between wait() & sleep()
Once I got a funny answer for the second question. "Sleep method makes the thread to sleep exactly for the specified amount of time and the wait method does it with some tolerance, ( the thread will sleep after some time ) " !!!