Also from the same site above, but more concerning lyrics.
How to Write Rap Lyrics - wikiHow
How to Write Rap Lyrics
So, you want to be a rapper? Before you can write a rap song, you need to know how to do the lyrics. You can't just rhyme one word with another. Here are some tips to help you get started.
Steps Think of a subject to help start your rap, for example the police, what you see, etc. Example: "da police i see you ima ridin round, in mi escalade you know im drivin round, and round. ok so lets go. police pull me over and i hit go let go they go cause i aint go money ill be back soon. with lots of cash man this is my tune."
Make sure the intro to your verse is strong. Set yourself up for a good rhyme scheme.
Man its strong palm down punch them get them ima strong man. Woman you too but you neva heard woman put it down like this 'for
Create a good rhyme scheme; you don't always need one but it helps. It helps the flow sound more enjoyable, example: 50 cent has a bounce flow, up and down, whereas Jay-Z goes side to side. This is important if you're making hits.
Notice that most rappers use multi-rhymes(example: Kill For, Still Roll). Put these at the end line after each bar and see how how hot your raps turn out. Count the syllables.
Let some of your friends read it and get their opinions, and if they have any suggestions write them down (get at least three friends opinions). When you get back to your writing area, redo the song with the suggestions from your friends and then go over it and make sure that the changes keep the flow.
Tips. Write the hook or chorus in a way that makes the listener really want to hear more of the song, but make sure the hook goes with the verses.
Just like you can be a good songwriter, but a poor singer, there is no shame if you can't rap the greatest lyrics you wrote. Get someone who can rap to test it out.
Deciding the title isn't really that big of a deal, but try to make it something out of the chorus.
Make sure to take your time on the song.
If you want you can even have your friends in your song to have more variety of lyrics.
Get a good book on writing lyrics, get some ideas from those.
Be real - rapping about your own life gives the song credibility.
Usually rap songs have at least two to three verses, but as long as your song makes the point you're trying to convey and is, in your opinion, good, length doesn't really matter.
If you ever have songwriters' block, listening to a couple of rap tunes can help give you fresh ideas.
Warnings. You can make up things in your lyrics, but make sure they don't single out any one specific person or group of persons.