The battle in hip-hop is an art form all to itself. In a freestyle battle, two rappers compete against each other in order to deliver the best rhymes. The object of the battle is to deliver funny and witty rhymes that tear down your opponent.
Some emcees will write rhymes and practice them just for battles, although this is not what a true rapper does. Freestyle means that you create your rhymes right there on the spot with no preparation.
If a rapper is truly freestyling, they should never repeat the same rhyme. It is like talking because most of the time you don’t rehearse what you are going to say.
I found this blog entry that delves into the topic with great detail and gives tips for any aspiring battler. Check it out!
http://noninedaywonder.blogspot.com/2007/10/how-to-survive-freestyle-rap-battle.html (Link no longer works)