I growl, so I don't think any of us are going to see people that teach you how to do that. I'd say your best bet would be to get a book or two and do some reading. However, practice and warming up is every bit as important with singing as anything else. That's the voice you talk with and unless you want to ruin that voice, it's important that you treat it well. Keep your throat well hydrated with plenty of water as well. I know there are plenty of techniques that you can do with you voice, but I haven't read into them enough to really describe how to use them or what they sound like, so, y'know.