1 - Focus on your opponent's clothing, lifestyle, parents, anything that is one of there weaknesses and make it into a rhyme.
2 - Practice a lot, if you don't, you won't get any better.
3 - Make your raps not just quick and insulting, but funny too, that will win the judges and crowd over quickly.
4 - Be a good sport if you lose. Don't curse or bitch out anyone.
5 - Have a good time, that's what rapping is all about. Look cool to get the audience excited!
6 - Speak clearly.It's not interesting when it sounds like you babbling.
7 - Wear cool clothes it'll impress the judges.
8 - Use gestures to match what you talking about.
9 - Try to go deep inside you, and then write whats on your heart, that would impress everybody.
10 - Try to get a sick beat that you can rap to.