Write your own lyrics:
You should start the journey from the most basic step and that is to get proper lyrics. The best way is to use your imagination and transform your thoughts into words. You must be observant and creative to write good lyrics. Do not use complex terms rather keep it simple as they will be easy to sing. Ultimately, a simple song will be an ideal stuff for fast rapping.
Memorise the lyrics:
Next thing you should do is to memorise the lyrics. You can become a fast rapper if you have a habit of reading from the paper. Moreover, memorising the lyrics will help you in understanding their meaning and you won’t find any difficulty to sing them at an amazing pace.
Practice all the time:
Practice, practice and practice some more to become a fast rapper. Remember, there is no shortcut to success to you must put an extra effort to be completely on song. If you are serious to pursue rapping as a career then religiously follow a training routine. No matter if you are travelling, resting on your bed or taking a shower; just keep yourself busy practicing.
Notice other professionals:
You must broaden your horizon and exposure. There are many professional rappers who are famous for their speed and skills. Eminem, Rebel XD, Tech N9ne, Twista and Busta Rhymes are the few prominent names in this list. You should check their work and try to learn the tricks of the trade.
Learn to makeup words:
You must learn how to fit in any word in a music piece or beat. There are no specific rules so you can make or break any word. You may create and use slang as well.