Know your speed of rapping which should be be fast enough maybe like 3-words per second (not a standard though). Then find a beat that matches with your speed of flow. Flow with the beat and if it doesn't move together find a suitable one. Be regular to the studio and practice frequently. If if moves well you'll know you're ready to have it produced.
For me, the beauty of rap lies in the beats, speed(fast and clear words), voice( kind of husky voice), the message and the motive. Try it...maybe it'll help. Nhialgatyung