When I am asked to answer the question "tell me about yourself" the following mayhem ensues:
1) I blurt out the first thing that comes to mind
2) Waffle on in an unstructured way for a long (long) time
3) Talk about totally irrelevant things
4) Clam up
It's embarrassing really.
Here are a few tips to tell people about yourself in a powerful way.
1) Keep your answer short - under 30 seconds if you can
2) Include an achievement statement to support what you say
3) Practice your answer until you are confident in what you say
4) Tailor your answer to the role at hand
5) Be genuinely enthusiastic about the opportunity at hand.
If you want to learn more, this article was a lot of help to me: http://interviewiq.com.au/tell-me-about-yourself