Take care of the professional voice. Many aspiring rappers believe that no skills of his own voice to rap is not need is a serious misconception. Of course, it is true for AK-47 or Gufa, however, such artists as Pencil, Vladi or Assai, by contrast, are always talking about the importance of continuous development of the vocal cords. The best way to understand and feel the possibility of his voice is a professional vocal that will teach you how to give "surround" sound and will help you to define your own range.
Copy and imitate. Of course, in the early stages you will be hard to write quality texts on their own, so try to duplicate the songs of famous artists and imitate their manner. Over time, you will go up, but initially, this approach can greatly help you.
Try yourself in different genres. Rap can be divided into many categories: lyrics, battlefie tracks, a philosophy or a pumping club hits. All has its own style of performance, and need to try everything to choose something for themselves. The lyrics has a more melodic character, so songs of this kind require elaborate vocal component, beautiful voice and getting into the tone of the music. Battlefie tracks are high speed recitative (sometimes even twice the normal "double-time"), so the performer has to be high diction. Club tracks the same aim to "rock the hall", so it is important to give the voice strength and volume to the same - to get exactly the bits, to accentuate the rhythm.
Communicate with experienced rappers and go to concerts. As you can see in the classroom singing, the man is very highly developed skill of "follow": when you hear the sound that you need to publish, then you do not understand how, probably will be able to repeat it. So, if you take patronage from someone more experienced "colleagues" you are copying "his sound", will understand how to acquire a proper supply.
Never worry that you have nothing. However, do not assume that something is too good. Self-esteem comes from experience.