Build your vocabulary. If you are going to be rhyming words, it is important that you have a few to pick from.
 Read books and news articles that contain polished, refined writing. If you come across a word you don't know, look it up
Develop an ear for rhythm. As you add to your vocabulary, 
try reading certain passages out loud and noticing where you naturally tend to add emphasis. 
In English, for example, a lot of poetry and song lyrics are written in iambic pentameter, 
in which the first syllable is unstressed, the second is stressed, the third is unstressed,
 and so on for a total of five stressed syllables and five unstressed syllables. 
Developing your sense of meter will ultimately help you form a beat to your lyrics, 
or the lyrics to your beat, in a way that sounds reflexive and easy.
Try saying "rapper" both ways, with the first syllable stressed and the second unstressed, 
then vice versa. Notice the difference?
It might sound dorky, but a good way to introduce yourself to iambic pentameter is to read Shakespeare aloud. 
(Search for his plays online.) You'll begin to notice the alternating stressed syllables and how naturally they flow.
Get focused. Your lyrics should have an objective other than making words rhyme. 
The rhyme is the glue for your lyrics, but the substance is in your message. 
What do you want to say? When you're talking to other people, which topics really get you fired up?
Whatever you choose, be real - rapping about your own life gives the song credibility.
Write it down. Rap lyrics can happen anywhere - at home, at work, at school, on the toilet, and in your sleep. 
Write down what comes to you without censoring yourself or editing. 
When you're struggling with writer's block later, refer back to your ideas.
Come up with a good hook. A hook is the part of a song that gets stuck in your head and makes you want to listen to it again.
 For most raps, this makes up the chorus. It doesn't have to be long, but it should have a catchy rhythm and be fun to hum.
Memorize your lyrics. After you have worked out a final draft of your rap lyrics, memorize every word. 
When you go to perform your rap song in the studio you don't want to be reading from your notebook.
Download an audio editing software: If you are a new rapper, it is recommended that you get Audacity. 
It is a freeware that is user-friendly and works quite well. If you own a Mac,
 you can record using Garage Band, which is already installed. After you gain more experience, 
it is recommended that you move onto other software such as Audio Audition. They are not free, but they are better than the free ones.
Revise to a beat. Pick a beat that you want to use to rap on. 
You can search for rap beats on youtube,
 or download rap beats from a beat distributor like Beat Brokerz.
A good strategy here is to already have the core of your rhymes written,
 and just work on adapting them to fit your beat. A common pitfall is if you try to write the core of your lyrics to a beat,
 you can likely suffer from "writers block" because you are trying to be creative and do revisions at the same time.
For a lot of songwriters, the hook is the most difficult part to create. 
Don't feel discouraged if it takes you awhile to come up with one 
- it's better to wait for a good hook than to wrap up your song with a bad one.