1. Just start “flowing” – rap is largely improvisational. Start by speaking. It doesn’t matter what you’re saying, just let the words come forward to get a feel for the medium and keep going.
2. As you become more adept, work traditional poetic techniques into your rap. Use metaphors to compare things and rhyme to give your verse a musical quality. Puns and wordplay make rap clever. Perhaps you can draw inspiration from the wise words of Ernest Hemingway, Dane Cook or Dr. Phil.
3. Practice, practice, practice. Rap as you walk to class – even if it’s about the gum you stepped in on or the baby birds you saw on the way. Keep building on the foundation you laid and you’ll be able to impress that sweet hunnie or bodacious babe you’ve had your eye on in no time.
4. Write a rap. Although rap started as improv, there is no law that says you can’t write it down ahead of time – doing so will allow for much more intricate and well-layered lyrics.
5. Have a rap battle. The ultimate test of your rapping abilities – and one of the fastest ways to hone your skills – is in competition with another rapper. Insults, clever jibes and lightning quick thinking are all elements in the rap battle, so practice with somebody who flows at about the same pace you do.
Information compiled from ehow.com