Think of a topic that you would like to rap about. Just like all songs and poetry, there is a central topic that is being expressed. For example, this could involve love, pain, happiness or greed. Refrain from rapping about the overused and negative topics of guns, drugs and womanizing.
Play an instrumental or a beat of a rap song. If you are unable to find an instrumental, then listening to the beat of a rap song with lyrics will work too. Go to the YouTube website to listen to some rap instrumentals. An instrumental will allow you to get your timing down. It is best to have your own beat so your lyrics will match up to it, and it can be original.
Begin your song by thinking of the chorus first. The chorus, or hook, is the part that is repeated throughout the song and is often the most memorable. This does not have to be complex. An example of a chorus could be: "Throughout my life, I have been dealt many cards, some of which have been very hard, but I'm not too far from getting what I want, turn the next one over cause it's to get a new start."
Start writing the first verse. Listen to the beat of the instrumental or envision a beat in your head and try to flow to it. Try to see how many words in one line you can rhyme. Some of the best rappers are able to rhyme each syllable and use multiple patterns of alliteration to develop a flow. If you are unable to do this, then try to rap at the end of every line or every other line.
Write a second verse and a third or fourth if you choose to do so. Typically, a rap verse consists of 40 bars or lines, although some may be slightly under or over this number. Finish the song by writing a bridge after you have written your verses. A bridge is a transition from the chorus and is usually only a few lines long. After the bridge, the chorus will repeat and another verse may come after it.