I posted this elsewhere about a year ago, but hopefully it helps ya:
What helped me the most when I was touring/recording:
A) taking breathing lessons.
B) watching singers I dug sing so I could emulate how they breathed and how their mouth and jaw shaped the tone
and
C) making sure I was relaxed - when I was uncomfortable or wound up or tense in any way it lead to a lot of vocal fatigue. When we were touring if I went on stage with my mind elsewhere (stressed at the booking agent, irritated by a douchebag club owner, mad at a girlfriend, whatevs) I could feel it in my throat the next day and if I did several gigs in a week like that after the third or fourth one I couldn't speak properly the following day. What helped the most was just fully buying in to the performance and shutting out everything else.
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Proper breathing is proper breathing. Doesn't matter if you're doing Death Metal, Djent or Disco. This video is totally not metal at all, but the info is sound and applicable:
https://www.youtube.com/watch?v=_BoAdlkLH_oWhat my old teacher had me do was inhale completely in one breath, then exhale in one. Then inhale in two even breathes, exhale in one, etc until I went through inhaling in six breathes, exhaling in one. Then starting over by exhaling in one, two, etc. ending with inhaling in six and exhaling in six. Then, I would practice holding my breath (I could routinely hold it for 3.5 minutes inhaled, 1.5 exhaled). After that, stretch your mouth and tongue by sticking your tongue out all the way to the right, then up, then left, then down and repeat. Took about 30 minutes to do all that, but at the end, I had way more power, control and far less fatigue. An added benefit is all that fresh oxygen really gets the rest of your body fired up and ready to go, too.
Last off, don't worry about trying to sound like someone else. The metal world doesn't need more clones, it needs you to be unique.