Here's a note of 5 things you should never do during an exit interview:
1. Tell the truth
Getting things off your chest never does any good in these situations. Remember, the HR bod or line manager who is conducting the interview is only doing so because they have to. The reality is that, in most cases, they already know full well why you are leaving
It's not cool to brandish your new offer letter, or reveal details of your new compensation package; you are tempting fate to slap you down at the first opportunity.
3. Be rude
Never be rude to anyone on the way up, as you never know when you may meet them again on the way back down.
4. Never take out your frustrations on the person interviewing you
The interviewer is only doing his / her job. They might be just as frustrated with the firm as you are.
5. Don't burn any bridges
As bad as you think things are at your current firm, the grass isn't always greener. Always leave a way back open.