Write... a lot. Don't get attached to any of it. Do 10, 15, 20 songs, put them out, move on and start more. Write through self-doubt. You probably suck right now and you'll probably suck for a long time, that's natural. It's a process. But don't ever judge yourself because you haven't written an Illmatic or a Ready To Die. Those are freaks of happenstance. Rap and all art in general is about evolution, not revolution. Be patient.