Arjun,
There are no right or wrong answers in an interview as opposed to an IQ test. You just have to be yourself and be as honest as you can while yet sounding positive and optimistic. If I may also add, be practical about your future. Try to project any mistakes in the past as stepping stones and learning milestones rather than deny you made the mistake at all! At the same time, use polite words while describing your previous organization or your ex-boss, even if he or she was a slave driver.
As for "tell me something about yourself"... well, tell them what you would like them to know. Share your special qualities, strengths, what kind of opportunities excite you, why you are considering them, what qualities and competencies that you possess seem to make a good fit, your other interests, etc. But avoid the temptation to parrot your CV (which is what most people do, and believe me, I have conducted hundreds of interviews, and it's quite boring and irritating!)
Again, remember, there is no right answer. You have to let the situation guide you. Good Luck!