If you want to do (good) death/thrash/black vocals, you should do this.
1.Sing clean, you will sound like shit but don't give a fuck (RHCP WILL HELP) sing californication and shit.
2. Sing louder and push your voice more, (this might hurt, hedonism will help)
3. try emulating your favorite singers and lose all fantasies of having perfect technique
4. remember attitude is everything, grow ball s you motherfucker faggit
5. BLACK 'N ROLL ,LISTEN TO MIDNIGHT AND TRY TO DOT THAT.
6(66).fuck i'm drunk, get a band together and do what the fuck you want to do, everoyne (including yourself will love it). Most importlantly, don't release anything that has a shitty commercial plastic sound. (be original enough, pls.)
Try to learn guitar or bass, will help with your note-ear.
Almost forgot the most important part, listen to all the singers you like and do what they do, the pain will go away if you do it enough, fuck all these snobs with perfect singing, except Iron Maiden. Drunken teenage faggot with a band signing off.