You can read 100 self help books for advices but at the end of
the day,
books are dead, you're alive, so dont rely too much on books.
You've to practise, practice, be shameless, be shameless 
If you have somethin to say, then say it. It's not a must to talk
to everyone.... Dont talk just for the sake of talking to change
yourself, it will appear weird & not natural (i know a person
whos like that....)
Confidence is the key!
For the competition right, dont think so low of yourself, neither
too high.
Just do your best during the competition and dont think too much
bout it. 
