Work on your abilities to rap and entertain. Keep up with trends, but that's what every other aspiring rapper will do. Always think of ways to make your brand of entertainment a little different than anything you've heard before.
Rap and perform where ever you can. This is the best way to develop the improvisational skills that are usually present in the stars. It also gets you in front of people whose acceptance or rejection of your work can be a guide to what you need to improve or change.
Educate yourself as much as possible. While it's certainly possible to "make it" without so much as a high school education, being well versed in English and other subjects can only expand your vocabulary and your range of subjects.
Put together a demo tape of your best tracks. It is up to you to find a studio and come up with the money to get this done.
Be willing to promote yourself at any venue possible. You will be one of thousands trying to get the attention of club and radio disc jockeys. Utilize social media. Make copies of your music and pass them out to try to spread word of mouth. Invest in high-quality publicity materials and get them in influential venues. Get to know other rappers and aspiring artists. There may be things you can teach each other, and another rapper may help you get your foot in the door of an agent or publicist.